From 83b9795ec96e7e326cc3dee4844a65b26b87604b Mon Sep 17 00:00:00 2001
From: Yoel Caspersen <yoel@kviknet.dk>
Date: Sun, 24 Oct 2021 15:02:15 +0200
Subject: [PATCH 1/7] Adding custom memcpy and memset functions to pass
 verifier checks Built-in memcpy and memset functions cause verifier to
 complain about misaligned stack access. To get around that (and be able to
 copy a dynamic number of bytes via memcpy), two custom functions are added.
 This version of the relay uses interface name + VLAN identifiers in option 82
 circuit ID (left-aligned, length IF_NAMESIZE with trailing null bytes).

Signed-off-by: Yoel Caspersen <yoel@kviknet.dk>
---
 dhcp-relay/Makefile        |   1 +
 dhcp-relay/dhcp-relay.h    |   4 +-
 dhcp-relay/dhcp_kern_xdp.c | 101 +++++++++++++++++++++++--------------
 3 files changed, 65 insertions(+), 41 deletions(-)

diff --git a/dhcp-relay/Makefile b/dhcp-relay/Makefile
index 964f707..6a3f5f6 100644
--- a/dhcp-relay/Makefile
+++ b/dhcp-relay/Makefile
@@ -4,6 +4,7 @@ USER_TARGETS := dhcp_user_xdp
 BPF_TARGETS :=dhcp_kern_xdp 
 EXTRA_DEPS := dhcp-relay.h
 #EXTRA_CFLAGS := $(if $(IPV6),-DIPV6)
+EXTRA_CFLAGS := -fno-builtin
 
 LIB_DIR = ../lib
 
diff --git a/dhcp-relay/dhcp-relay.h b/dhcp-relay/dhcp-relay.h
index 09bca44..ab7fec9 100644
--- a/dhcp-relay/dhcp-relay.h
+++ b/dhcp-relay/dhcp-relay.h
@@ -10,7 +10,7 @@
 #define DHO_DHCP_AGENT_OPTIONS 82
 #define RAI_CIRCUIT_ID 1
 #define RAI_REMOTE_ID 2
-#define RAI_OPTION_LEN 40
+#define RAI_OPTION_LEN IF_NAMESIZE
 #define VLAN_ASCII_MAX 4  /* Max bytes needed to store VLAN in ASCII format */
 
 #define DHCP_SERVER_PORT 67
@@ -22,7 +22,7 @@
 struct sub_option {
 	__u8 option_id;
 	__u8 len;
-	char val[IF_NAMESIZE];
+	char val[RAI_OPTION_LEN];
 };
 
 /*structure for dhcp option 82 */
diff --git a/dhcp-relay/dhcp_kern_xdp.c b/dhcp-relay/dhcp_kern_xdp.c
index 56cd040..d19bae2 100644
--- a/dhcp-relay/dhcp_kern_xdp.c
+++ b/dhcp-relay/dhcp_kern_xdp.c
@@ -8,6 +8,13 @@
 #include <xdp/context_helpers.h>
 #include "dhcp-relay.h"
 
+#define bpf_printk(fmt, ...)                                    \
+({                                                              \
+        char ____fmt[] = fmt;                                   \
+        bpf_trace_printk(____fmt, sizeof(____fmt),              \
+                         ##__VA_ARGS__);                        \
+})
+
 /*
  * This map is for storing the DHCP relay configuration, including:
  * 
@@ -49,35 +56,63 @@ struct {
 	__uint(max_entries, 16384);
 } client_vlans SEC(".maps");
 
+void memcpy_var(void *to, void *from, __u64 len) {
+	__u8 *t8 = to, *f8 = from;
+	int i;
+
+	for (i = 0; i < len; i++) {
+		*t8++ = *f8++;		
+	}
+		
+}
+
+void memset_var(void *d, __u8 c, __u64 len) {
+	__u8 *d8 = d;
+	int i;
+
+	for (i = 0; i < len; i++) {
+		*d8++ = c;
+	}
+		
+}
+
 /* Inserts DHCP option 82 into the received DHCP packet
  * at the specified offset.
  */
 static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	struct collect_vlans *vlans, char *dev) {
+	
 	struct dhcp_option_82 option;
-
+	
 	option.t = DHO_DHCP_AGENT_OPTIONS;
 	option.len = sizeof (struct sub_option) + sizeof (struct sub_option);
 	option.circuit_id.option_id = RAI_CIRCUIT_ID;
-	option.circuit_id.len = sizeof(option.circuit_id.val);
+	option.circuit_id.len = sizeof (option.circuit_id.val);
+	option.remote_id.option_id = RAI_REMOTE_ID;
+	option.remote_id.len = sizeof (option.remote_id.val);
+
+	/* Initialize val arrays */
+	memset_var(option.circuit_id.val, 0, sizeof (option.circuit_id.val));
+	memset_var(option.remote_id.val, '*', sizeof (option.remote_id.val));
+	//memset(option.circuit_id.val, 0, sizeof (option.circuit_id.val));
+	//memset(option.remote_id.val, '*', sizeof (option.remote_id.val));
 	
 	/* Reconstruct VLAN device name
 	 * Convert VLAN tags to ASCII from right to left, starting with
 	 * inner VLAN tag.
-	 * Device name is 16 characters long and prepended with dash, e.g.:
-	 * ----ens6f0.83.20
-	 * We avoid null bytes to ensure compatibility with DHCP servers that
-	 * interpret null as a string terminator.
+	 * Device name is up to 16 characters long - remaining buffer space
+	 * contains null bytes.
 	 */
-	 
-	char buf[IF_NAMESIZE];
-	memset(buf, '-', sizeof (buf));
+
+	char buf[RAI_OPTION_LEN];
+	memset(buf, 0, sizeof (buf));
 	
-	int c = VLAN_ASCII_MAX;		/* We will need 4 bytes at most */
-	int i = IF_NAMESIZE - 1;
+	int c = VLAN_ASCII_MAX; /* We will need 4 bytes at most */
+	int i = RAI_OPTION_LEN - 1;
 	__u16 inner_vlan = vlans->id[1];
 	__u16 outer_vlan = vlans->id[0];
-	
+
+	/* Convert inner VLAN to ASCII */
 	for (c = VLAN_ASCII_MAX; c > 0; c--) {
 		buf[i--] = (inner_vlan % 10) + '0';
 		inner_vlan /= 10;
@@ -85,9 +120,10 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 			break;
 		}
 	}
-	
+
 	buf[i--] = '.';
-	
+
+	/* Convert outer VLAN to ASCII */
 	for (c = VLAN_ASCII_MAX; c > 0; c--) {
 		buf[i--] = (outer_vlan % 10) + '0';
 		outer_vlan /= 10;
@@ -95,31 +131,25 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 			break;
 		}
 	}
-	
+
 
 	buf[i--] = '.';
-	
-	for (c = IF_NAMESIZE - 1; c >= 0; c--) {
 
-		if (dev[c] != 0) {
+	/* Append interface name */
+	for (c = RAI_OPTION_LEN - 1; c >= 0; c--) {
+		if (dev[c] != 0)
 			buf[i--] = dev[c];
-		}
-		
-		if (i < 0) {
-			break;
-		}
-
-	}
-
-	if(sizeof(option.circuit_id.val) == sizeof(buf)) {
-		memcpy(option.circuit_id.val, buf, sizeof(buf));
+		if (i < 0)
+			break;	
 	}
 	
-	/* Initialize remote ID */
-	memset(option.remote_id.val, 0, sizeof(option.remote_id.val));
-	option.remote_id.option_id = RAI_REMOTE_ID;
-	option.remote_id.len = sizeof(option.remote_id.val);
+	i++;
 	
+	/* Copy resulting interface name to circuit_id */
+	if (sizeof (option.circuit_id.val) == sizeof (buf)) {
+		memcpy_var(option.circuit_id.val, buf + i, sizeof (buf) - i);
+	}
+
 	return xdp_store_bytes(ctx, offset, &option, sizeof (option), 0);
 }
 
@@ -166,13 +196,6 @@ static __always_inline int calc_ip_csum(struct iphdr *oldip, struct iphdr *ip,
  */
 //static __u8 buf[static_offset + VLAN_MAX_DEPTH * sizeof (struct vlan_hdr)];
 
-#define bpf_printk(fmt, ...)                                    \
-({                                                              \
-        char ____fmt[] = fmt;                                   \
-        bpf_trace_printk(____fmt, sizeof(____fmt),              \
-                         ##__VA_ARGS__);                        \
-})
-
 /* XDP program for parsing the DHCP packet and inserting the option 82*/
 SEC(XDP_PROG_SEC)
 int xdp_dhcp_relay(struct xdp_md *ctx) {

From 8d91b1409e3050da7e1fb3c3a9672ce95883e982 Mon Sep 17 00:00:00 2001
From: Yoel Caspersen <yoel@kviknet.dk>
Date: Mon, 25 Oct 2021 22:23:16 +0200
Subject: [PATCH 2/7] Upstream direction works with QinQ packets only When
 allowing packets with 1 VLAN tag only, verifier complains about BPF program
 being too large. Compiled with LLVM 13.

Signed-off-by: Yoel Caspersen <yoel@kviknet.dk>
---
 dhcp-relay/dhcp-relay.h    |  2 ++
 dhcp-relay/dhcp_kern_xdp.c | 47 +++++++++++++++++++++++++-------------
 2 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/dhcp-relay/dhcp-relay.h b/dhcp-relay/dhcp-relay.h
index ab7fec9..00cd7ea 100644
--- a/dhcp-relay/dhcp-relay.h
+++ b/dhcp-relay/dhcp-relay.h
@@ -18,6 +18,8 @@
 #define DHCP_REQUEST 1
 #define DHCP_REPLY 2
 
+#define MAX_LOOPS 40
+
 /* Structure for sub-options in option 82 */
 struct sub_option {
 	__u8 option_id;
diff --git a/dhcp-relay/dhcp_kern_xdp.c b/dhcp-relay/dhcp_kern_xdp.c
index d19bae2..27df8ba 100644
--- a/dhcp-relay/dhcp_kern_xdp.c
+++ b/dhcp-relay/dhcp_kern_xdp.c
@@ -60,7 +60,7 @@ void memcpy_var(void *to, void *from, __u64 len) {
 	__u8 *t8 = to, *f8 = from;
 	int i;
 
-	for (i = 0; i < len; i++) {
+	for (i = 0; i < len && i < MAX_LOOPS; i++) {
 		*t8++ = *f8++;		
 	}
 		
@@ -70,7 +70,7 @@ void memset_var(void *d, __u8 c, __u64 len) {
 	__u8 *d8 = d;
 	int i;
 
-	for (i = 0; i < len; i++) {
+	for (i = 0; i < len && i < MAX_LOOPS; i++) {
 		*d8++ = c;
 	}
 		
@@ -84,6 +84,8 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	
 	struct dhcp_option_82 option;
 	
+	static __u8 buf[RAI_OPTION_LEN];
+	
 	option.t = DHO_DHCP_AGENT_OPTIONS;
 	option.len = sizeof (struct sub_option) + sizeof (struct sub_option);
 	option.circuit_id.option_id = RAI_CIRCUIT_ID;
@@ -104,15 +106,16 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	 * contains null bytes.
 	 */
 
-	char buf[RAI_OPTION_LEN];
 	memset(buf, 0, sizeof (buf));
 	
 	int c = VLAN_ASCII_MAX; /* We will need 4 bytes at most */
 	int i = RAI_OPTION_LEN - 1;
+	
 	__u16 inner_vlan = vlans->id[1];
 	__u16 outer_vlan = vlans->id[0];
 
 	/* Convert inner VLAN to ASCII */
+#pragma unroll VLAN_ASCII_MAX
 	for (c = VLAN_ASCII_MAX; c > 0; c--) {
 		buf[i--] = (inner_vlan % 10) + '0';
 		inner_vlan /= 10;
@@ -124,6 +127,7 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	buf[i--] = '.';
 
 	/* Convert outer VLAN to ASCII */
+#pragma unroll VLAN_ASCII_MAX	
 	for (c = VLAN_ASCII_MAX; c > 0; c--) {
 		buf[i--] = (outer_vlan % 10) + '0';
 		outer_vlan /= 10;
@@ -132,10 +136,10 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 		}
 	}
 
-
 	buf[i--] = '.';
 
 	/* Append interface name */
+#pragma unroll RAI_OPTION_LEN
 	for (c = RAI_OPTION_LEN - 1; c >= 0; c--) {
 		if (dev[c] != 0)
 			buf[i--] = dev[c];
@@ -148,8 +152,9 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	/* Copy resulting interface name to circuit_id */
 	if (sizeof (option.circuit_id.val) == sizeof (buf)) {
 		memcpy_var(option.circuit_id.val, buf + i, sizeof (buf) - i);
+		//memcpy_var(option.circuit_id.val, buf, sizeof (buf));
 	}
-
+	
 	return xdp_store_bytes(ctx, offset, &option, sizeof (option), 0);
 }
 
@@ -206,10 +211,10 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	int res = bpf_xdp_adjust_tail(ctx, delta);
 	if (res != 0) {
 		bpf_printk("Cannot tail extend packet, delta %i - error code %i", delta, res);
-		return XDP_ABORTED;
+		return XDP_PASS;
 	}
 
-	bpf_printk("Tail extended packet by %i bytes", delta);
+	//bpf_printk("Tail extended packet by %i bytes", delta);
 
 	void *data_end = (void *) (long) ctx->data_end;
 	void *data = (void *) (long) ctx->data;
@@ -240,27 +245,34 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	int key = 0;
 	int len = 0;
 
-	if (data + 1 > data_end)
-		return XDP_ABORTED;
+	if (data + 1 > data_end) {
+		bpf_printk("Empty packet\n");
+		goto out;
+	}
 
 	nh.pos = data;
 	ether_type = parse_ethhdr_vlan(&nh, data_end, &eth, &vlans);
 	/* check for valid ether type */
 	if (ether_type < 0) {
-		bpf_printk("Cannot determine ethertype");
-		rc = XDP_ABORTED;
+		bpf_printk("Cannot determine ethertype\n");
 		goto out;
 	}
+	
 	if (ether_type != bpf_htons(ETH_P_IP)) {
-		bpf_printk("Ethertype %#x is not ETH_P_IP", bpf_ntohs(ether_type));
+		//bpf_printk("Ethertype %x is not ETH_P_IP\n", bpf_ntohs(ether_type));
 		goto out;
 	}
 
-	bpf_printk("Ethertype %x", bpf_ntohs(ether_type));
-
+	bpf_printk("Ethertype %x\n", bpf_ntohs(ether_type));
+	
 	/* Check at least two vlan tags are present */
+	if (vlans.id[0] == 0) {
+		bpf_printk("No outer VLAN tag set\n");
+		goto out;
+	}
+	
 	if (vlans.id[1] == 0) {
-		bpf_printk("No VLAN tags set");
+		bpf_printk("No inner VLAN tag set\n");
 		goto out;
 	}
 
@@ -287,6 +299,8 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 	/* Increase UDP length header */
 	udp->len += bpf_htons(delta);
+	
+	udp->check = 0;
 
 	/* Read DHCP server IP from config map */
 	key = 0;
@@ -317,6 +331,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	//	goto out;
 
 	/* Increment offset by 4 bytes for each VLAN (to accomodate VLAN headers */
+#pragma unroll VLAN_MAX_DEPTH
 	for (i = 0; i < VLAN_MAX_DEPTH; i++) {
 		if (vlans.id[i]) {
 
@@ -449,7 +464,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 				bpf_printk("Could not write DHCP option 82 at offset %i", option_offset);
 				return XDP_ABORTED;
 			}
-
+			
 			/* Set END option */
 
 			/* Verifier check */

From 17f1da535f6d27c95e826eceb5e5993de87e52df Mon Sep 17 00:00:00 2001
From: Yoel Caspersen <yoel@kviknet.dk>
Date: Fri, 5 Nov 2021 14:36:44 +0100
Subject: [PATCH 3/7] First working prototype (IPv4 DHCP relay works in both
 directions)

In this version of the relay, we assume that client requests are
received on a double tagged VLAN interface and server replies are
received on a single tagged VLAN interface.

Test scripts are added:

- test.sh (configures BNG and sets L3 config)
- cleanup_test.sh (removes BNG configuration)
- trace.sh (opens trace pipe for debugging)

The code for adding interface name is disabled because it makes the
verifier complain about the BPF program being too large.

To-do:
- Fix verifier issue to include interface name in option 82
- For server replies, erase option 82 instead of (partial) overwrite

Signed-off-by: Yoel Caspersen <yoel@kviknet.dk>
---
 dhcp-relay/cleanup_test.sh |  27 +++
 dhcp-relay/dhcp-relay.h    |   5 +-
 dhcp-relay/dhcp_kern_xdp.c | 398 ++++++++++++++++++++++++-------------
 dhcp-relay/test.sh         |  65 ++++++
 dhcp-relay/trace.sh        |   3 +
 5 files changed, 356 insertions(+), 142 deletions(-)
 create mode 100755 dhcp-relay/cleanup_test.sh
 create mode 100755 dhcp-relay/test.sh
 create mode 100755 dhcp-relay/trace.sh

diff --git a/dhcp-relay/cleanup_test.sh b/dhcp-relay/cleanup_test.sh
new file mode 100755
index 0000000..d7ae11e
--- /dev/null
+++ b/dhcp-relay/cleanup_test.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+# -x
+
+OUTER_VLAN=83
+INNER_VLAN=20
+UPLINK_VLAN=84
+IF="ens6f0"
+
+DHCP_SERVER="185.107.12.59"
+IPADDR_BNG="194.45.77.57"
+IPADDR_UPLINK="185.107.12.99"
+CLIENT_IP="194.45.77.59"
+
+echo "Unloading XDP program"
+./dhcp_user_xdp -i $IF -d $DHCP_SERVER -s $IPADDR_BNG -u
+
+echo "Deleting VLAN interfaces"
+# Delete inner VLAN interface
+ip link del $IF.$OUTER_VLAN.$INNER_VLAN
+# Delete outer VLAN interface
+ip link del $IF.$OUTER_VLAN
+
+echo "Deleting uplink interface"
+ip link del $IF.$UPLINK_VLAN
+
+# Remove BNG address from loopback interface
+ip addr del $IPADDR_BNG/29 dev lo
\ No newline at end of file
diff --git a/dhcp-relay/dhcp-relay.h b/dhcp-relay/dhcp-relay.h
index 00cd7ea..32b84bb 100644
--- a/dhcp-relay/dhcp-relay.h
+++ b/dhcp-relay/dhcp-relay.h
@@ -18,7 +18,10 @@
 #define DHCP_REQUEST 1
 #define DHCP_REPLY 2
 
-#define MAX_LOOPS 40
+#define MAX_LOOPS 20
+#define U16_ASCII_LEN 5	/* Max value: 65535 */
+
+#define IP_ADDR_BCAST 0xFFFFFFFF	/* 255.255.255.255 in hex */
 
 /* Structure for sub-options in option 82 */
 struct sub_option {
diff --git a/dhcp-relay/dhcp_kern_xdp.c b/dhcp-relay/dhcp_kern_xdp.c
index 27df8ba..df74750 100644
--- a/dhcp-relay/dhcp_kern_xdp.c
+++ b/dhcp-relay/dhcp_kern_xdp.c
@@ -56,36 +56,93 @@ struct {
 	__uint(max_entries, 16384);
 } client_vlans SEC(".maps");
 
-void memcpy_var(void *to, void *from, __u64 len) {
+static int memcpy_var(void *to, void *from, __u8 len) {
 	__u8 *t8 = to, *f8 = from;
 	int i;
 
-	for (i = 0; i < len && i < MAX_LOOPS; i++) {
-		*t8++ = *f8++;		
+	if (len > MAX_LOOPS) {
+		return -1;
 	}
-		
+
+	for (i = 0; i < len; i++) {
+
+		if (i > MAX_LOOPS) {
+			return -1;
+		}
+
+		*t8++ = *f8++;
+
+	}
+
+
+	if (i == MAX_LOOPS)
+		return -1;
+
+	return 0;
+
 }
 
-void memset_var(void *d, __u8 c, __u64 len) {
-	__u8 *d8 = d;
-	int i;
+static int u16_to_ascii(char *buf, __u8 offset, __u16 num) {
+
+	__u8 i;
+#pragma unroll U16_ASCII_LEN
+	for (i = offset; i > 0; i--) {
+
+		buf[i - 1] = (num % 10) + '0';
+		num /= 10;
+		if (num == 0)
+			break;
 
-	for (i = 0; i < len && i < MAX_LOOPS; i++) {
-		*d8++ = c;
 	}
-		
+
+	if (i > 1) {
+		i--;
+		buf[i - 1] = '.';
+	}
+
+	return i - 1;
+
+}
+
+static int str_len(char *buf) {
+
+	__u8 i = 0;
+	for (i = 0; i < IF_NAMESIZE; i++)
+		if (buf[i] == 0)
+			break;
+
+	return i;
+
+}
+
+static int copy_dev_name(char *buf, __u8 offset, char dev[IF_NAMESIZE]) {
+
+	__u8 dev_len = 0;
+
+	dev_len = str_len(dev);
+	
+	/* Check if we have enough space in buffer */
+	if ((offset - dev_len) < 0) {
+		return -1;
+	}
+	
+	offset -= dev_len;
+	
+	memcpy_var(buf + offset, dev, dev_len);
+	
+	return offset;
 }
 
 /* Inserts DHCP option 82 into the received DHCP packet
  * at the specified offset.
  */
 static __always_inline int write_dhcp_option_82(void *ctx, int offset,
-	struct collect_vlans *vlans, char *dev) {
-	
-	struct dhcp_option_82 option;
-	
-	static __u8 buf[RAI_OPTION_LEN];
-	
+		struct collect_vlans *vlans, char dev[IF_NAMESIZE]) {
+
+	struct dhcp_option_82 option = {0};
+
+	static __u8 buf[RAI_OPTION_LEN] = {0};
+
 	option.t = DHO_DHCP_AGENT_OPTIONS;
 	option.len = sizeof (struct sub_option) + sizeof (struct sub_option);
 	option.circuit_id.option_id = RAI_CIRCUIT_ID;
@@ -93,12 +150,6 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	option.remote_id.option_id = RAI_REMOTE_ID;
 	option.remote_id.len = sizeof (option.remote_id.val);
 
-	/* Initialize val arrays */
-	memset_var(option.circuit_id.val, 0, sizeof (option.circuit_id.val));
-	memset_var(option.remote_id.val, '*', sizeof (option.remote_id.val));
-	//memset(option.circuit_id.val, 0, sizeof (option.circuit_id.val));
-	//memset(option.remote_id.val, '*', sizeof (option.remote_id.val));
-	
 	/* Reconstruct VLAN device name
 	 * Convert VLAN tags to ASCII from right to left, starting with
 	 * inner VLAN tag.
@@ -106,55 +157,49 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	 * contains null bytes.
 	 */
 
-	memset(buf, 0, sizeof (buf));
-	
-	int c = VLAN_ASCII_MAX; /* We will need 4 bytes at most */
-	int i = RAI_OPTION_LEN - 1;
-	
+	int i = RAI_OPTION_LEN;
+
+	// Start with interface name
+	/*int dev_len = str_len(dev, IF_NAMESIZE);
+	if (dev_len < sizeof (option.circuit_id.val)) {
+		memcpy_var(option.circuit_id.val, dev, dev_len);
+	}*/
+
 	__u16 inner_vlan = vlans->id[1];
 	__u16 outer_vlan = vlans->id[0];
 
-	/* Convert inner VLAN to ASCII */
-#pragma unroll VLAN_ASCII_MAX
-	for (c = VLAN_ASCII_MAX; c > 0; c--) {
-		buf[i--] = (inner_vlan % 10) + '0';
-		inner_vlan /= 10;
-		if (inner_vlan == 0) {
-			break;
+	if (inner_vlan != 0) {
+
+		/* Convert inner VLAN to ASCII */
+		i = u16_to_ascii(buf, RAI_OPTION_LEN, inner_vlan);
+		if (i < 0) {
+			return -1;
 		}
+
 	}
 
-	buf[i--] = '.';
+	if (outer_vlan != 0) {
 
-	/* Convert outer VLAN to ASCII */
-#pragma unroll VLAN_ASCII_MAX	
-	for (c = VLAN_ASCII_MAX; c > 0; c--) {
-		buf[i--] = (outer_vlan % 10) + '0';
-		outer_vlan /= 10;
-		if (outer_vlan == 0) {
-			break;
+		/* Convert outer VLAN to ASCII */
+		i = u16_to_ascii(buf, i, outer_vlan);
+		if (i < 0) {
+			return -1;
 		}
+
 	}
 
-	buf[i--] = '.';
+// FIXME: Verifier complains about BPF program being too large when this
+// function is enabled
+//	i = copy_dev_name(buf, i, dev);
+//	if (i < 0)
+//		return -1;
 
-	/* Append interface name */
-#pragma unroll RAI_OPTION_LEN
-	for (c = RAI_OPTION_LEN - 1; c >= 0; c--) {
-		if (dev[c] != 0)
-			buf[i--] = dev[c];
-		if (i < 0)
-			break;	
-	}
-	
-	i++;
-	
-	/* Copy resulting interface name to circuit_id */
 	if (sizeof (option.circuit_id.val) == sizeof (buf)) {
+		
+		/* Copy right-aligned VLAN text to left-aligned buffer */
 		memcpy_var(option.circuit_id.val, buf + i, sizeof (buf) - i);
-		//memcpy_var(option.circuit_id.val, buf, sizeof (buf));
 	}
-	
+
 	return xdp_store_bytes(ctx, offset, &option, sizeof (option), 0);
 }
 
@@ -171,10 +216,10 @@ static __always_inline int write_dhcp_option_255(void *ctx, int offset) {
 
 /* Calculates the IP checksum */
 static __always_inline int calc_ip_csum(struct iphdr *oldip, struct iphdr *ip,
-	__u32 oldcsum) {
+		__u32 oldcsum) {
 	__u32 size = sizeof (struct iphdr);
 	__u32 csum = bpf_csum_diff((__be32 *) oldip, size, (__be32 *) ip, size,
-		~oldcsum);
+			~oldcsum);
 	__u32 sum = (csum >> 16) + (csum & 0xffff);
 	sum += (sum >> 16);
 	return sum;
@@ -189,7 +234,7 @@ static __always_inline int calc_ip_csum(struct iphdr *oldip, struct iphdr *ip,
 	sizeof(struct ethhdr) + sizeof(struct iphdr) + sizeof(struct udphdr) + \
 		offsetof(struct dhcp_packet, options)
 
-/* Delta value to be adjusted at xdp head*/
+/* Delta value for tail adjustment */
 #define delta sizeof(struct dhcp_option_82)
 
 #ifndef DHCP_MAX_OPTIONS
@@ -205,8 +250,6 @@ static __always_inline int calc_ip_csum(struct iphdr *oldip, struct iphdr *ip,
 SEC(XDP_PROG_SEC)
 int xdp_dhcp_relay(struct xdp_md *ctx) {
 
-	bpf_printk("\n");
-
 	/* Tail extend packet */
 	int res = bpf_xdp_adjust_tail(ctx, delta);
 	if (res != 0) {
@@ -236,7 +279,8 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	__u8 option_length = 0;
 	__u64 client_mac = 0;
 	char *dev;
-	int i = 0;
+	__u8 i = 0;
+	__u8 head_adjusted = 0;
 
 	/* These keep track of the next header type and iterator pointer */
 	struct hdr_cursor nh;
@@ -246,7 +290,6 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	int len = 0;
 
 	if (data + 1 > data_end) {
-		bpf_printk("Empty packet\n");
 		goto out;
 	}
 
@@ -254,32 +297,31 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	ether_type = parse_ethhdr_vlan(&nh, data_end, &eth, &vlans);
 	/* check for valid ether type */
 	if (ether_type < 0) {
-		bpf_printk("Cannot determine ethertype\n");
+		bpf_printk("Cannot determine ethertype");
 		goto out;
 	}
-	
+
 	if (ether_type != bpf_htons(ETH_P_IP)) {
-		//bpf_printk("Ethertype %x is not ETH_P_IP\n", bpf_ntohs(ether_type));
+		//bpf_printk("Ethertype %x is not ETH_P_IP", bpf_ntohs(ether_type));
 		goto out;
 	}
 
-	bpf_printk("Ethertype %x\n", bpf_ntohs(ether_type));
-	
-	/* Check at least two vlan tags are present */
+	/* Check at least one vlan tag is present */
 	if (vlans.id[0] == 0) {
-		bpf_printk("No outer VLAN tag set\n");
+		bpf_printk("No outer VLAN tag set");
 		goto out;
 	}
-	
+
 	if (vlans.id[1] == 0) {
-		bpf_printk("No inner VLAN tag set\n");
-		goto out;
+		bpf_printk("No inner VLAN tag set");
+		//goto out;
 	}
 
 	h_proto = parse_iphdr(&nh, data_end, &ip);
 
 	/* Only handle fixed-size IP header due to static copy */
 	if (h_proto != IPPROTO_UDP || ip->ihl > 5) {
+		bpf_printk("Not UDP");
 		goto out;
 	}
 
@@ -291,15 +333,17 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 		goto out;
 
 	/* Handle DHCP packets only */
-	if (udp->dest != bpf_htons(DHCP_SERVER_PORT) && udp->dest != bpf_htons(DHCP_CLIENT_PORT))
+	if (udp->dest != bpf_htons(DHCP_SERVER_PORT) && udp->dest != bpf_htons(DHCP_CLIENT_PORT)) {
+		bpf_printk("Not DHCP");
 		goto out;
+	}
 
 	/* Increase IP length header */
 	ip->tot_len += bpf_htons(delta);
 
 	/* Increase UDP length header */
 	udp->len += bpf_htons(delta);
-	
+
 	udp->check = 0;
 
 	/* Read DHCP server IP from config map */
@@ -326,9 +370,8 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	if (dev == NULL)
 		goto out;
 
-	/* Copy headers of packet to buf */
-	//if (xdp_load_bytes(ctx, 0, buf, static_offset))
-	//	goto out;
+	//memcpy(dev_name, dev, IF_NAMESIZE);
+	//dev_len = str_len(dev_name, IF_NAMESIZE);
 
 	/* Increment offset by 4 bytes for each VLAN (to accomodate VLAN headers */
 #pragma unroll VLAN_MAX_DEPTH
@@ -337,9 +380,6 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 			bpf_printk("Found VLAN tag %i at depth %i", vlans.id[i], i);
 
-			/* For each VLAN present, copy 4 bytes of DHCP options to buffer */
-			//if (xdp_load_bytes(ctx, offset, buf + offset, 4))
-			//	goto out;
 			offset += 4;
 			vlan_length += 4;
 		}
@@ -355,6 +395,16 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	}
 	dhcp = data + vlan_length + dhcp_offset;
 
+	/* Check hops */
+	if (dhcp->hops > 16) {
+		bpf_printk("Max hops exceeded, discarding packet");
+		rc = XDP_ABORTED;
+		goto out;
+	}
+
+	/* Increment hops */
+	dhcp->hops++;
+
 	/* Store client MAC */
 	if (dhcp->chaddr + ETH_ALEN > data_end) {
 		goto out;
@@ -364,11 +414,11 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	bpf_printk("Parsing DHCP packet, opcode %i, hops %i", dhcp->op, dhcp->hops);
 
 	if (dhcp->op == DHCP_REQUEST && (eth->h_dest[0] == 0xff
-		&& eth->h_dest[1] == 0xff
-		&& eth->h_dest[2] == 0xff
-		&& eth->h_dest[3] == 0xff
-		&& eth->h_dest[4] == 0xff
-		&& eth->h_dest[5] == 0xff)) {
+			&& eth->h_dest[1] == 0xff
+			&& eth->h_dest[2] == 0xff
+			&& eth->h_dest[3] == 0xff
+			&& eth->h_dest[4] == 0xff
+			&& eth->h_dest[5] == 0xff)) {
 
 		/* Request from client received as broadcast */
 
@@ -395,25 +445,16 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 
 	} else if (dhcp->op == DHCP_REPLY && (eth->h_dest[0] != 0xff
-		|| eth->h_dest[1] != 0xff
-		|| eth->h_dest[2] != 0xff
-		|| eth->h_dest[3] != 0xff
-		|| eth->h_dest[4] != 0xff
-		|| eth->h_dest[5] != 0xff)) {
+			|| eth->h_dest[1] != 0xff
+			|| eth->h_dest[2] != 0xff
+			|| eth->h_dest[3] != 0xff
+			|| eth->h_dest[4] != 0xff
+			|| eth->h_dest[5] != 0xff)) {
 
 		/* Response from server received as unicast */
 
 		bpf_printk("Unicast packet received, opcode %i, hops %i", dhcp->op, dhcp->hops);
 
-		/* FIXME: Add code for reply packets
-		 * Basically:
-		 * - Set dest and src MAC
-		 * - Add VLAN tags
-		 * - Remove option 82
-		 * - Use XDP_TX (or XDP_REDIRECT) to send the response
-		 * to the end user
-		 */
-
 		struct collect_vlans *new_vlans;
 		new_vlans = bpf_map_lookup_elem(&client_vlans, &client_mac);
 		if (new_vlans == NULL) {
@@ -421,19 +462,89 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 			goto out;
 		}
 
-		bpf_printk("Found map entry for MAC %i", client_mac);
+		bpf_printk("Found map entry for MAC %x", client_mac);
 
-	}
+		/* Set destination MAC */
+		memcpy(eth->h_dest, dhcp->chaddr, ETH_ALEN);
 
-	/* Check hops */
-	if (dhcp->hops > 16) {
-		bpf_printk("Max hops exceeded, discarding packet");
-		rc = XDP_ABORTED;
-		goto out;
-	}
+		/* Set source MAC */
+		memcpy(eth->h_source, relay_hwaddr, ETH_ALEN);
 
-	/* Increment hops */
-	dhcp->hops++;
+		/* Set destination IP */
+		ip->daddr = IP_ADDR_BCAST;
+
+		/* Set source IP */
+		ip->saddr = *relay_agent_ip;
+
+		/* Add / replace VLAN tags */
+		if (vlans.id[0] != 0) {
+			bpf_printk("Outer VLAN %i found, will change to %i", vlans.id[0], new_vlans->id[0]);
+
+			struct vlan_hdr *outer_vlh = data + ETH_HLEN;
+			outer_vlh->h_vlan_TCI = bpf_htons((bpf_ntohs(outer_vlh->h_vlan_TCI) & 0xf000) | new_vlans->id[0]);
+
+		}
+
+		if (vlans.id[1] != 0) {
+			bpf_printk("Inner VLAN %i found, will change to %i", vlans.id[1], new_vlans->id[1]);
+
+			struct vlan_hdr *inner_vlh = data + ETH_HLEN + sizeof (struct vlan_hdr);
+			inner_vlh->h_vlan_TCI = bpf_htons((bpf_ntohs(inner_vlh->h_vlan_TCI) & 0xf000) | new_vlans->id[1]);
+
+		} else {
+			bpf_printk("Inner VLAN not found, will insert %i", new_vlans->id[1]);
+
+			/* Adjust header by -4 bytes to make space for VLAN header */
+			if (bpf_xdp_adjust_head(ctx, -(int) sizeof (struct vlan_hdr))) {
+				bpf_printk("Cannot head-adjust packet by %i bytes, aborting", -(int) sizeof (struct vlan_hdr));
+				rc = XDP_ABORTED;
+				goto out;
+			}
+
+			bpf_printk("Head-adjusted packet by %i bytes", -(int) sizeof (struct vlan_hdr));
+
+			head_adjusted = 1;
+
+			data_end = (void *) (long) ctx->data_end;
+			data = (void *) (long) ctx->data;
+
+			/* Verifier check */
+			if (data + ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr) + sizeof (struct vlan_hdr) > data_end) {
+				rc = XDP_ABORTED;
+				goto out;
+			}
+			
+			/* Move MAC address headers + outer VLAN tag to beginning of packet */
+			memmove(data, data + sizeof (struct vlan_hdr), ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr));
+
+			bpf_printk("Moved %i bytes from offset %i to offset %i", ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr), sizeof (struct vlan_hdr), 0);
+
+			/* Make new inner VLAN header (copy from outer VLAN header) */
+			memcpy(data + ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr), data + ETH_ALEN + ETH_ALEN, sizeof (struct vlan_hdr));
+
+			bpf_printk("Copied %i bytes from offset %i to offset %i", sizeof (struct vlan_hdr), ETH_ALEN + ETH_ALEN, ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr));
+
+			bpf_printk("Will modify VLAN header at offset %i", ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr));
+
+			struct vlan_hdr *vlh = data + ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr) + 2;
+			vlh->h_vlan_TCI = bpf_htons((bpf_ntohs(vlh->h_vlan_TCI) & 0xf000) | new_vlans->id[1]);
+
+			offset += sizeof (struct vlan_hdr);
+			vlan_length += sizeof (struct vlan_hdr);
+
+			/* Parse DHCP packet */
+			if (data + vlan_length + dhcp_offset + sizeof (dhcp) > data_end) {
+				goto out;
+			}
+			dhcp = data + vlan_length + dhcp_offset;
+
+			bpf_printk("Inserted VLAN header");
+
+		}
+
+		rc = XDP_TX;
+
+	}
 
 	/* Check if we exceed boundaries to make verifier happy */
 	if (data + offset > data_end)
@@ -451,20 +562,33 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 		if (pos + 1 > data_end)
 			break;
 
+		/* Read option code */
 		option_code = *pos;
 
 		bpf_printk("Got option code %i at offset %i, hex %x", option_code, option_offset, option_offset);
 
+		if (option_code == 82 && dhcp->op == DHCP_REPLY) {
+
+			bpf_printk("Will erase DHCP option 82");
+
+			/* FIXME: Erase options 82 + 255 and set new option 255 */
+
+			*pos = 255;
+			break;
+
+		}
+
 		if (option_code == 255) {
 
-			bpf_printk("Going to write DHCP option at offset %i", option_offset);
+			bpf_printk("Going to write DHCP option 82 at offset %i", option_offset);
 
 			/* Insert Option 82 before END option */
 			if (write_dhcp_option_82(ctx, option_offset, &vlans, dev)) {
 				bpf_printk("Could not write DHCP option 82 at offset %i", option_offset);
-				return XDP_ABORTED;
+				//return XDP_ABORTED;
+				break;
 			}
-			
+
 			/* Set END option */
 
 			/* Verifier check */
@@ -476,57 +600,50 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 			if (write_dhcp_option_255(ctx, option_offset)) {
 				bpf_printk("Could not write DHCP option 255 at offset %i", option_offset);
-				return XDP_ABORTED;
+				//return XDP_ABORTED;
+				break;
 			}
 
 			bpf_printk("Wrote DHCP option 255 at offset %i, returning XDP_PASS", option_offset);
 
 			break;
 		}
+
 		pos++;
 
+		/* Verifier check */
+		if (pos + 1 > data_end) {
+			break;
+		}
+
 		option_length = *pos;
 		option_offset += option_length + 2;
 
+		/* Verifier check */
 		if (pos + 1 > data_end) {
 			break;
 		}
 		pos++;
 
+		/* Verifier check */
 		if (pos + option_length > data_end) {
 			break;
 		}
+
+		/* Skip option value (go to next option) */
 		pos += option_length;
 
 	}
 
-	//return XDP_PASS;
-
-	/* Copy stored headers from buf to context */
-	/*if (xdp_store_bytes(ctx, 0, buf, static_offset, 0)) {
-
-		bpf_printk("xdp_store_bytes(ctx, 0, buf, %i) failed", static_offset);
-		return XDP_ABORTED;
-	}*/
-
-
-	/* make space for option 82 - copy DHCP options after increasing offset */
-	/*if (offset > static_offset) {
-		offset = static_offset;
-		for (i = 0; i < VLAN_MAX_DEPTH; i++) {
-			if (vlans.id[i]) {*/
-	/*  */
-	/*if (xdp_store_bytes(ctx, offset, buf + offset,
-		4, 0))
-		return XDP_ABORTED;
-	offset += 4;
-}
+	/* Adjust IP offset for VLAN header when VLAN header has been added */
+	if (head_adjusted) {
+		ip = data + ip_offset + sizeof (struct vlan_hdr);
+	} else {
+		ip = data + ip_offset;
 	}
-	}*/
-
-	ip = data + ip_offset;
-	if (ip + 1 > data_end)
+	if (ip + 1 > data_end) {
 		return XDP_ABORTED;
+	}
 
 	/* Overwrite the destination IP in IP header */
 	ip->daddr = *dhcp_srv_ip;
@@ -537,7 +654,6 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	/* Re-calculate ip checksum */
 	__u32 sum = calc_ip_csum(&oldip, ip, oldip.check);
 	ip->check = ~sum;
-	rc = XDP_PASS;
 
 	goto out;
 
diff --git a/dhcp-relay/test.sh b/dhcp-relay/test.sh
new file mode 100755
index 0000000..dc5f026
--- /dev/null
+++ b/dhcp-relay/test.sh
@@ -0,0 +1,65 @@
+#!/bin/bash -x
+
+OUTER_VLAN=83
+INNER_VLAN=20
+UPLINK_VLAN=84
+IF="ens6f0"
+
+DHCP_SERVER="185.107.12.59"
+IPADDR_BNG="194.45.77.57"
+IPADDR_UPLINK="185.107.12.99"
+UPLINK_GW="185.107.12.97"
+CLIENT_IP="194.45.77.59"
+
+echo "Setting up VLAN interfaces"
+ethtool -K $IF txvlan off
+ethtool -K $IF rxvlan off
+# Increase MTU to allow second VLAN tag (QinQ)
+ip link set dev $IF mtu 1504
+ip link set dev $IF up
+# Set outer VLAN interface
+ip link add link $IF name $IF.$OUTER_VLAN type vlan id $OUTER_VLAN
+ip link set $IF.$OUTER_VLAN up
+
+CLIENT_IF=$IF.$OUTER_VLAN.$INNER_VLAN
+
+# Set inner VLAN interface
+ip link add link $IF.$OUTER_VLAN name $CLIENT_IF type vlan id $INNER_VLAN
+ip link set $CLIENT_IF up
+
+# Set accept_local for VLAN interface
+echo 1 > /proc/sys/net/ipv4/conf/$CLIENT_IF/accept_local
+
+# Disable reverse path filtering for VLAN interface
+echo 0 > /proc/sys/net/ipv4/conf/$CLIENT_IF/rp_filter
+
+# Enable ARP proxy for VLAN interface
+echo 1 > /proc/sys/net/ipv4/conf/$CLIENT_IF/proxy_arp
+
+# Insert /32 route to client
+ip route add $CLIENT_IP/32 dev $CLIENT_IF
+
+# Set IP forwarding
+echo 1 > /proc/sys/net/ipv4/ip_forward
+
+# Set L3 config for BNG interface
+ip addr add $IPADDR_BNG/29 dev lo
+
+# Create upstream interface
+ip link add link $IF name $IF.$UPLINK_VLAN type vlan id $UPLINK_VLAN
+ip link set dev $IF.$UPLINK_VLAN
+ip link set $IF.$UPLINK_VLAN up
+
+# Disable RP filtering globally to receive DHCP requests through unnumbered
+# interface
+echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter
+
+# Set L3 config for upstream interface
+ip addr add $IPADDR_UPLINK/28 dev $IF.$UPLINK_VLAN
+ip route replace default via $UPLINK_GW
+
+echo "Compiling XDP program"
+make
+
+echo "Launching XDP program"
+./dhcp_user_xdp -i $IF -d $DHCP_SERVER -s $IPADDR_UPLINK
\ No newline at end of file
diff --git a/dhcp-relay/trace.sh b/dhcp-relay/trace.sh
new file mode 100755
index 0000000..d364282
--- /dev/null
+++ b/dhcp-relay/trace.sh
@@ -0,0 +1,3 @@
+#!/bin/bash -x
+
+cat /sys/kernel/debug/tracing/trace_pipe
\ No newline at end of file

From 813cfa271928f8482d0d3788eae6df6d452ee9cf Mon Sep 17 00:00:00 2001
From: Yoel Caspersen <yoel@kviknet.dk>
Date: Tue, 9 Nov 2021 16:35:37 +0100
Subject: [PATCH 4/7] Working prototype (IPv4) with interface name in Option 82
 Circuit ID

This version works with kernel 5.15 and LLVM 13.

Improvements:

- Interface name is added to Option 82 Circuit ID
- On server replies, Option 82 is wiped completely
- Char array parameters replaced with structs

Functions that previously used char arrays as function parameters now
use structs instead - otherwise the verifier cannot perform proper
boundary checks.

To-do:
- IPv6 support
- Multiple interface support

Signed-off-by: Yoel Caspersen <yoel@kviknet.dk>
---
 dhcp-relay/dhcp-relay.h    |   5 +
 dhcp-relay/dhcp_kern_xdp.c | 187 +++++++++++++++++++++----------------
 dhcp-relay/dhcp_user_xdp.c |  88 +++--------------
 3 files changed, 129 insertions(+), 151 deletions(-)

diff --git a/dhcp-relay/dhcp-relay.h b/dhcp-relay/dhcp-relay.h
index 32b84bb..8345786 100644
--- a/dhcp-relay/dhcp-relay.h
+++ b/dhcp-relay/dhcp-relay.h
@@ -43,6 +43,11 @@ struct dhcp_option_255 {
 	__u8 t;
 };
 
+struct dev_name {
+	char name[IF_NAMESIZE];
+	__u8 len;
+};
+
 struct dhcp_packet {
 	__u8 op; /* 0: Message opcode/type */
 	__u8 htype; /* 1: Hardware addr type (net/if_types.h) */
diff --git a/dhcp-relay/dhcp_kern_xdp.c b/dhcp-relay/dhcp_kern_xdp.c
index df74750..d54b2ab 100644
--- a/dhcp-relay/dhcp_kern_xdp.c
+++ b/dhcp-relay/dhcp_kern_xdp.c
@@ -1,8 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
+#include <net/if.h>    /* IF_NAMESIZE */
 #include <linux/bpf.h>
 #include <linux/in.h>
-#include <net/if.h>    /* IF_NAMESIZE */
 #include <bpf/bpf_helpers.h>
 #include <xdp/parsing_helpers.h>
 #include <xdp/context_helpers.h>
@@ -56,80 +56,107 @@ struct {
 	__uint(max_entries, 16384);
 } client_vlans SEC(".maps");
 
-static int memcpy_var(void *to, void *from, __u8 len) {
-	__u8 *t8 = to, *f8 = from;
-	int i;
-
-	if (len > MAX_LOOPS) {
-		return -1;
-	}
-
-	for (i = 0; i < len; i++) {
-
-		if (i > MAX_LOOPS) {
-			return -1;
-		}
-
-		*t8++ = *f8++;
-
-	}
+//static int memcpy_var(void *to, void *from, __u8 len) {
+//	__u8 *t8 = to, *f8 = from;
+//	int i;
+//
+//	if (len > RAI_OPTION_LEN) {
+//		return -1;
+//	}
+//
+//	for (i = 0; i < len; i++) {
+//
+//		if (i > RAI_OPTION_LEN) {
+//			return -1;
+//		}
+//
+//		*t8++ = *f8++;
+//
+//	}
+//
+//
+//	if (i == RAI_OPTION_LEN)
+//		return -1;
+//
+//	return 0;
+//
+//}
 
+int u16_to_ascii(struct sub_option *opt, __u8 offset, __u16 num) {
 
-	if (i == MAX_LOOPS)
+	if (opt == NULL)
 		return -1;
 
-	return 0;
-
-}
+	if (offset > RAI_OPTION_LEN)
+		return -1;
 
-static int u16_to_ascii(char *buf, __u8 offset, __u16 num) {
+	if (offset < U16_ASCII_LEN)
+		return -1;
 
 	__u8 i;
-#pragma unroll U16_ASCII_LEN
-	for (i = offset; i > 0; i--) {
+	//#pragma unroll U16_ASCII_LEN
+	for (i = offset - 1; i > 0; i--) {
 
-		buf[i - 1] = (num % 10) + '0';
+		if (i == 0)
+			break;
+
+		opt->val[i] = (__u8) (num % 10) + '0';
 		num /= 10;
 		if (num == 0)
 			break;
 
 	}
 
-	if (i > 1) {
-		i--;
-		buf[i - 1] = '.';
+	if (i > 0) {
+		opt->val[--i] = '.';
 	}
 
-	return i - 1;
+	if (i > RAI_OPTION_LEN)
+		return -1;
+
+	return i;
 
 }
 
-static int str_len(char *buf) {
+int str_len(struct dev_name *dev) {
+
+	if (dev == NULL)
+		return -1;
 
 	__u8 i = 0;
-	for (i = 0; i < IF_NAMESIZE; i++)
-		if (buf[i] == 0)
+	for (i = 0; i < RAI_OPTION_LEN; i++)
+		if (dev->name[i] == 0)
 			break;
 
 	return i;
 
 }
 
-static int copy_dev_name(char *buf, __u8 offset, char dev[IF_NAMESIZE]) {
+int copy_dev_name(struct sub_option *dest, __u8 offset, struct dev_name *dev) {
 
-	__u8 dev_len = 0;
+	if (dest == NULL)
+		return -1;
 
-	dev_len = str_len(dev);
-	
-	/* Check if we have enough space in buffer */
-	if ((offset - dev_len) < 0) {
+	if (dev == NULL)
 		return -1;
+
+	__u8 i;
+
+	/* Copy device name and left-align VLAN part*/
+#pragma unroll RAI_OPTION_LEN
+	for (i = 0; i < RAI_OPTION_LEN; i++) {
+
+		if (i < dev->len) {
+			/* Copy device name */
+			dest->val[i] = dev->name[i];
+		} else if (offset < RAI_OPTION_LEN) {
+			/* Move VLAN part (all bytes from offset and up) */
+			dest->val[i] = dest->val[offset];
+			dest->val[offset++] = 0;
+		}
+
 	}
-	
-	offset -= dev_len;
-	
-	memcpy_var(buf + offset, dev, dev_len);
-	
+
 	return offset;
 }
 
@@ -137,12 +164,10 @@ static int copy_dev_name(char *buf, __u8 offset, char dev[IF_NAMESIZE]) {
  * at the specified offset.
  */
 static __always_inline int write_dhcp_option_82(void *ctx, int offset,
-		struct collect_vlans *vlans, char dev[IF_NAMESIZE]) {
+		struct collect_vlans *vlans, struct dev_name dev) {
 
 	struct dhcp_option_82 option = {0};
 
-	static __u8 buf[RAI_OPTION_LEN] = {0};
-
 	option.t = DHO_DHCP_AGENT_OPTIONS;
 	option.len = sizeof (struct sub_option) + sizeof (struct sub_option);
 	option.circuit_id.option_id = RAI_CIRCUIT_ID;
@@ -159,19 +184,13 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 
 	int i = RAI_OPTION_LEN;
 
-	// Start with interface name
-	/*int dev_len = str_len(dev, IF_NAMESIZE);
-	if (dev_len < sizeof (option.circuit_id.val)) {
-		memcpy_var(option.circuit_id.val, dev, dev_len);
-	}*/
-
 	__u16 inner_vlan = vlans->id[1];
 	__u16 outer_vlan = vlans->id[0];
 
 	if (inner_vlan != 0) {
 
 		/* Convert inner VLAN to ASCII */
-		i = u16_to_ascii(buf, RAI_OPTION_LEN, inner_vlan);
+		i = u16_to_ascii(&option.circuit_id, RAI_OPTION_LEN, inner_vlan);
 		if (i < 0) {
 			return -1;
 		}
@@ -181,24 +200,17 @@ static __always_inline int write_dhcp_option_82(void *ctx, int offset,
 	if (outer_vlan != 0) {
 
 		/* Convert outer VLAN to ASCII */
-		i = u16_to_ascii(buf, i, outer_vlan);
+		i = u16_to_ascii(&option.circuit_id, i, outer_vlan);
 		if (i < 0) {
 			return -1;
 		}
 
 	}
 
-// FIXME: Verifier complains about BPF program being too large when this
-// function is enabled
-//	i = copy_dev_name(buf, i, dev);
-//	if (i < 0)
-//		return -1;
-
-	if (sizeof (option.circuit_id.val) == sizeof (buf)) {
-		
-		/* Copy right-aligned VLAN text to left-aligned buffer */
-		memcpy_var(option.circuit_id.val, buf + i, sizeof (buf) - i);
-	}
+	/* Insert device name and left-align circuit ID */
+	i = copy_dev_name(&option.circuit_id, i, &dev);
+	if (i < 0)
+		return -1;
 
 	return xdp_store_bytes(ctx, offset, &option, sizeof (option), 0);
 }
@@ -267,6 +279,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	struct iphdr oldip;
 	struct udphdr *udp;
 	struct dhcp_packet *dhcp;
+	struct dev_name dev = {0};
 	__u32 *dhcp_srv_ip;
 	__u32 *relay_agent_ip;
 	__u64 *relay_hwaddr;
@@ -278,7 +291,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 	__u8 option_code = 0;
 	__u8 option_length = 0;
 	__u64 client_mac = 0;
-	char *dev;
+	char *dev_config;
 	__u8 i = 0;
 	__u8 head_adjusted = 0;
 
@@ -295,9 +308,9 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 	nh.pos = data;
 	ether_type = parse_ethhdr_vlan(&nh, data_end, &eth, &vlans);
-	/* check for valid ether type */
+	/* Check for valid EtherType */
 	if (ether_type < 0) {
-		bpf_printk("Cannot determine ethertype");
+		bpf_printk("Cannot determine EtherType");
 		goto out;
 	}
 
@@ -314,7 +327,6 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 	if (vlans.id[1] == 0) {
 		bpf_printk("No inner VLAN tag set");
-		//goto out;
 	}
 
 	h_proto = parse_iphdr(&nh, data_end, &ip);
@@ -366,12 +378,12 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 	/* Read device name from device map */
 	key = 0;
-	dev = bpf_map_lookup_elem(&device_name, &key);
-	if (dev == NULL)
+	dev_config = bpf_map_lookup_elem(&device_name, &key);
+	if (dev_config == NULL)
 		goto out;
 
-	//memcpy(dev_name, dev, IF_NAMESIZE);
-	//dev_len = str_len(dev_name, IF_NAMESIZE);
+	memcpy(dev.name, dev_config, RAI_OPTION_LEN);
+	dev.len = str_len(&dev);
 
 	/* Increment offset by 4 bytes for each VLAN (to accomodate VLAN headers */
 #pragma unroll VLAN_MAX_DEPTH
@@ -513,7 +525,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 				rc = XDP_ABORTED;
 				goto out;
 			}
-			
+
 			/* Move MAC address headers + outer VLAN tag to beginning of packet */
 			memmove(data, data + sizeof (struct vlan_hdr), ETH_ALEN + ETH_ALEN + sizeof (struct vlan_hdr));
 
@@ -552,10 +564,12 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 	option_offset = offset;
 
+	__u8 n = 0;
+
 	__u8 *pos = (__u8 *) (data + option_offset);
 
 	/* Loop through all DHCP options */
-#pragma unroll DHCP_MAX_OPTIONS
+	//#pragma unroll DHCP_MAX_OPTIONS
 	for (i = 0; i < DHCP_MAX_OPTIONS; i++) {
 
 		/* Verifier check */
@@ -571,9 +585,26 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
 			bpf_printk("Will erase DHCP option 82");
 
-			/* FIXME: Erase options 82 + 255 and set new option 255 */
-
+			/* Set new option 255 */
 			*pos = 255;
+
+			/* Increment pointer 2nd byte of option 82 */
+			pos++;
+
+			/* Verifier check */
+			if (pos + 1 > data_end)
+				break;
+
+			/* Erase remainder of option 82 */
+			for (n = 0; n < sizeof (struct dhcp_option_82); n++) {
+
+				if (pos + 1 > data_end)
+					break;
+
+				*pos++ = 0;
+
+			}
+
 			break;
 
 		}
diff --git a/dhcp-relay/dhcp_user_xdp.c b/dhcp-relay/dhcp_user_xdp.c
index 2aeb56e..a2ea5e5 100644
--- a/dhcp-relay/dhcp_user_xdp.c
+++ b/dhcp-relay/dhcp_user_xdp.c
@@ -89,63 +89,8 @@ int xdp_link_attach(int ifindex, __u32 xdp_flags, int prog_fd) {
 	return 0;
 }
 
-/* User program takes two  or three arguments
- * interface name, relay server IP and prog
- * unload flag
- */
 int main(int argc, char **argv) {
 
-	/*char device[500] = "ens6f0np0";
-	char o82[30] = { 0 };
-	
-	int outer_vlan = 80;
-	int inner_vlan = 25;
-
-	char str[30] = {0}; // large enough for an int even on 64-bit
-	int i = 30;
-	int c = 0;
-
-	for(c = 4; c > 0; c--) {
-		str[i--] = (inner_vlan % 10) + '0';
-		inner_vlan /= 10;
-		if(inner_vlan == 0) {
-			break;
-		}
-	}
-	
-	str[i--] = '.';
-	
-	for(c = 4; c > 0; c--) {
-		str[i--] = (outer_vlan % 10) + '0';
-		outer_vlan /= 10;
-		if(outer_vlan == 0) {
-			break;
-		}
-	}
-	
-	str[i--] = '.';
-	
-	int y;
-	for(y = sizeof(device) - 1; y >= 0; y--) {
-		if(device[y] != 0) {
-			str[i] = device[y];
-			i--;
-		}
-	}
-	
-	printf("i is %i\n", i);
-	
-	memset(o82, 0, 30);
-	memcpy(o82, str + i + 1, 30 - i);
-	
-	printf("The number was: %s\n", str + i + 1);
-
-	printf("Option 82: %s\n", o82);
-	
-	printf("Option 82 length was %i\n", 30 - i);
-	
-	return 0;*/
-
 	char filename[256] = "dhcp_kern_xdp.o";
 	int prog_fd, err;
 	int opt;
@@ -171,7 +116,7 @@ int main(int argc, char **argv) {
 	while ((opt = getopt_long(argc, argv, "hui:d:m:s:", options, NULL)) !=
 		-1) {
 		switch (opt) {
-			case 'i':
+			case 'i':	/* Physical interface */
 				strncpy(dev, optarg, IF_NAMESIZE);
 				dev[IF_NAMESIZE - 1] = '\0';
 				ifindex = if_nametoindex(dev);
@@ -180,7 +125,7 @@ int main(int argc, char **argv) {
 					return -EINVAL;
 				}
 				break;
-			case 'd': // DHCP server address
+			case 'd':	/* DHCP server address */
 				if (inet_aton(optarg, &dhcp_server_addr) == 0) {
 					fprintf(stderr,
 						"Couldn't validate DHCP server IP address:%s\n",
@@ -189,7 +134,7 @@ int main(int argc, char **argv) {
 				}
 				dhcp_server_addr_set = true;
 				break;
-			case 's': // Relay agent address
+			case 's':	/* Relay agent address */
 				if (inet_aton(optarg, &relay_agent_addr) == 0) {
 					fprintf(stderr,
 						"Couldn't validate relay agent IP address:%s\n",
@@ -198,7 +143,7 @@ int main(int argc, char **argv) {
 				}
 				relay_agent_addr_set = true;
 				break;
-			case 'm':
+			case 'm':	/* Mode: skb or native */
 				if (strcmp(optarg, "skb") == 0) {
 					xdp_flags = XDP_FLAGS_SKB_MODE;
 				} else if (strcmp(optarg, "drv") != 0) {
@@ -207,10 +152,10 @@ int main(int argc, char **argv) {
 				}
 
 				break;
-			case 'u':
+			case 'u':	/* Unload XDP program */
 				do_unload = 1;
 				break;
-			case 'h':
+			case 'h':	/* Help menu */
 				print_usage(argv);
 				exit(0);
 			default:
@@ -235,7 +180,7 @@ int main(int argc, char **argv) {
 	if (do_unload)
 		return xdp_link_detach(ifindex, xdp_flags);
 
-	// Find MAC address of interface
+	/* Find MAC address of interface */
 	fd = socket(AF_INET, SOCK_DGRAM, 0);
 
 	ifr.ifr_addr.sa_family = AF_INET;
@@ -250,7 +195,7 @@ int main(int argc, char **argv) {
 	__u64 hwaddr = 0;
 	memcpy(&hwaddr, (unsigned char *) ifr.ifr_hwaddr.sa_data, 6);
 
-	//display mac address
+	/* Display MAC address */
 	printf("Using device %s MAC: %.2x:%.2x:%.2x:%.2x:%.2x:%.2x\n", dev, mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
 
 	/* Load the BPF-ELF object file and get back first BPF_prog FD */
@@ -265,9 +210,7 @@ int main(int argc, char **argv) {
 		return -1;
 	}
 
-	/* read the map from prog object file and update the real
-	 * server IP to the map
-	 */
+	/* Open server config map */
 	map = bpf_object__find_map_by_name(obj, SERVER_MAP);
 	err = libbpf_get_error(map);
 	if (err) {
@@ -282,7 +225,7 @@ int main(int argc, char **argv) {
 		exit(-1);
 	}
 
-	// Set DHCP server address
+	/* Set DHCP server address */
 	key = 0;
 	err = bpf_map_update_elem(map_fd, &key, &dhcp_server_addr.s_addr, BPF_ANY);
 	if (err) {
@@ -291,7 +234,7 @@ int main(int argc, char **argv) {
 		exit(-1);
 	}
 
-	// Set relay agent IP address
+	/* Set relay agent IP address */
 	key = 1;
 	err = bpf_map_update_elem(map_fd, &key, &relay_agent_addr.s_addr, BPF_ANY);
 	if (err) {
@@ -300,7 +243,7 @@ int main(int argc, char **argv) {
 		exit(-1);
 	}
 
-	// Set relay agent MAC address
+	/* Set relay agent MAC address */
 	key = 2;
 	err = bpf_map_update_elem(map_fd, &key, &hwaddr, BPF_ANY);
 	if (err) {
@@ -310,9 +253,7 @@ int main(int argc, char **argv) {
 	}
 
 
-	/* read the map from prog object file and update the real
-	 * server IP to the map
-	 */
+	/* Open device map */
 	device_map = bpf_object__find_map_by_name(obj, DEVICE_MAP);
 	err = libbpf_get_error(device_map);
 	if (err) {
@@ -327,7 +268,7 @@ int main(int argc, char **argv) {
 		exit(-1);
 	}
 
-	// Set device name in map
+	/* Set device name in map */
 	key = 0;
 	err = bpf_map_update_elem(device_map_fd, &key, dev, BPF_ANY);
 	if (err) {
@@ -336,6 +277,7 @@ int main(int argc, char **argv) {
 		exit(-1);
 	}
 
+	/* Attach XDP program to interface */
 	err = xdp_link_attach(ifindex, xdp_flags, prog_fd);
 	if (err)
 		return err;

From f26620260ae25eee733b9cf77cda63dc1493970d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Sat, 13 Nov 2021 00:00:40 +0100
Subject: [PATCH 5/7] Improve readability of write_dhcp_option_82()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This makes several changes to improve the readability of write_dhcp_option_82():

The main change is in reworking the string helpers to be smaller and more
modular, and using a separate buffer for stringifying the VLAN tags before
copying them to the DHCP option field. Get rid of str_len() and the len
member of struct dev_name. To aid in this, the whole containing function is
made global (i.e., a separate BPF subprog) instead of the helpers.

In addition, the local variables are renamed to be more descriptive, and
the option struct is initialised using struct initialisation syntax.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 dhcp-relay/dhcp-relay.h    |   1 -
 dhcp-relay/dhcp_kern_xdp.c | 187 ++++++++++++-------------------------
 2 files changed, 58 insertions(+), 130 deletions(-)

diff --git a/dhcp-relay/dhcp-relay.h b/dhcp-relay/dhcp-relay.h
index 8345786..cbda2f0 100644
--- a/dhcp-relay/dhcp-relay.h
+++ b/dhcp-relay/dhcp-relay.h
@@ -45,7 +45,6 @@ struct dhcp_option_255 {
 
 struct dev_name {
 	char name[IF_NAMESIZE];
-	__u8 len;
 };
 
 struct dhcp_packet {
diff --git a/dhcp-relay/dhcp_kern_xdp.c b/dhcp-relay/dhcp_kern_xdp.c
index d54b2ab..6b45d36 100644
--- a/dhcp-relay/dhcp_kern_xdp.c
+++ b/dhcp-relay/dhcp_kern_xdp.c
@@ -56,163 +56,93 @@ struct {
 	__uint(max_entries, 16384);
 } client_vlans SEC(".maps");
 
-//static int memcpy_var(void *to, void *from, __u8 len) {
-//	__u8 *t8 = to, *f8 = from;
-//	int i;
-//
-//	if (len > RAI_OPTION_LEN) {
-//		return -1;
-//	}
-//
-//	for (i = 0; i < len; i++) {
-//
-//		if (i > RAI_OPTION_LEN) {
-//			return -1;
-//		}
-//
-//		*t8++ = *f8++;
-//
-//	}
-//
-//
-//	if (i == RAI_OPTION_LEN)
-//		return -1;
-//
-//	return 0;
-//
-//}
-
-int u16_to_ascii(struct sub_option *opt, __u8 offset, __u16 num) {
-
-	if (opt == NULL)
-		return -1;
-
-	if (offset > RAI_OPTION_LEN)
-		return -1;
+static int u16_to_ascii(struct dev_name *buf, __u8 end_offset, __u16 num) {
+	int i;
 
-	if (offset < U16_ASCII_LEN)
+	if (buf == NULL ||
+	    end_offset > sizeof(buf->name) ||
+	    end_offset < U16_ASCII_LEN)
 		return -1;
 
-	__u8 i;
-	//#pragma unroll U16_ASCII_LEN
-	for (i = offset - 1; i > 0; i--) {
-
-		if (i == 0)
-			break;
-
-		opt->val[i] = (__u8) (num % 10) + '0';
+	for (i = end_offset - 1; i >= 0; i--) {
+		buf->name[i] = (__u8) (num % 10) + '0';
 		num /= 10;
-		if (num == 0)
+		if (!num)
 			break;
-
 	}
 
-	if (i > 0) {
-		opt->val[--i] = '.';
-	}
-
-	if (i > RAI_OPTION_LEN)
-		return -1;
-
 	return i;
-
 }
 
-int str_len(struct dev_name *dev) {
+static int copy_dev_name(struct sub_option *dest, __u8 wr_offset,
+			 struct dev_name *dev, __u8 rd_offset) {
+	int i;
 
-	if (dev == NULL)
+	if (dest == NULL || dev == NULL || wr_offset > sizeof(dest->val) - 1)
 		return -1;
 
-	__u8 i = 0;
-	for (i = 0; i < RAI_OPTION_LEN; i++)
-		if (dev->name[i] == 0)
+	for (i = 0; i < sizeof(dest->val) - wr_offset - 1; i++) {
+		if (i + rd_offset > sizeof(dev->name) - 1 ||
+		    !dev->name[i + rd_offset])
 			break;
 
-	return i;
-
-}
-
-int copy_dev_name(struct sub_option *dest, __u8 offset, struct dev_name *dev) {
-
-	if (dest == NULL)
-		return -1;
-
-	if (dev == NULL)
-		return -1;
-
-	__u8 i;
-
-	/* Copy device name and left-align VLAN part*/
-#pragma unroll RAI_OPTION_LEN
-	for (i = 0; i < RAI_OPTION_LEN; i++) {
-
-		if (i < dev->len) {
-			/* Copy device name */
-			dest->val[i] = dev->name[i];
-		} else if (offset < RAI_OPTION_LEN) {
-			/* Move VLAN part (all bytes from offset and up) */
-			dest->val[i] = dest->val[offset];
-			dest->val[offset++] = 0;
-		}
-
+		dest->val[i + wr_offset] = dev->name[i + rd_offset];
 	}
 
-	return offset;
+ 	return i;
 }
 
 /* Inserts DHCP option 82 into the received DHCP packet
  * at the specified offset.
  */
-static __always_inline int write_dhcp_option_82(void *ctx, int offset,
-		struct collect_vlans *vlans, struct dev_name dev) {
-
-	struct dhcp_option_82 option = {0};
-
-	option.t = DHO_DHCP_AGENT_OPTIONS;
-	option.len = sizeof (struct sub_option) + sizeof (struct sub_option);
-	option.circuit_id.option_id = RAI_CIRCUIT_ID;
-	option.circuit_id.len = sizeof (option.circuit_id.val);
-	option.remote_id.option_id = RAI_REMOTE_ID;
-	option.remote_id.len = sizeof (option.remote_id.val);
-
-	/* Reconstruct VLAN device name
-	 * Convert VLAN tags to ASCII from right to left, starting with
-	 * inner VLAN tag.
-	 * Device name is up to 16 characters long - remaining buffer space
-	 * contains null bytes.
-	 */
-
-	int i = RAI_OPTION_LEN;
-
-	__u16 inner_vlan = vlans->id[1];
-	__u16 outer_vlan = vlans->id[0];
+int write_dhcp_option_82(struct xdp_md *ctx, int pkt_offset,
+			 struct collect_vlans *vlans, struct dev_name *dev) {
+
+	__u16 inner_vlan, outer_vlan;
+	struct dev_name buf = {};
+	int len, vlan_offset;
+	struct dhcp_option_82 option = {
+		.t = DHO_DHCP_AGENT_OPTIONS,
+		.len = sizeof (struct sub_option) + sizeof (struct sub_option),
+		.circuit_id.option_id = RAI_CIRCUIT_ID,
+		.circuit_id.len = sizeof (option.circuit_id.val),
+		.remote_id.option_id = RAI_REMOTE_ID,
+		.remote_id.len = sizeof (option.remote_id.val)
+	};
+
+	if (!ctx || !vlans || !dev)
+		return -1;
 
-	if (inner_vlan != 0) {
+	inner_vlan = vlans->id[1];
+	outer_vlan = vlans->id[0];
 
-		/* Convert inner VLAN to ASCII */
-		i = u16_to_ascii(&option.circuit_id, RAI_OPTION_LEN, inner_vlan);
-		if (i < 0) {
-			return -1;
-		}
+	if (!inner_vlan || !outer_vlan)
+		return -1;
 
-	}
+	/* The u16_to_ascii function works backwards from the end of the buffer,
+	 * so start out at the end of the string.
+	 */
+	vlan_offset = sizeof(buf.name);
 
-	if (outer_vlan != 0) {
+	vlan_offset = u16_to_ascii(&buf, vlan_offset, inner_vlan);
+	if (vlan_offset < 0)
+		return vlan_offset;
+	buf.name[--vlan_offset] = '.';
 
-		/* Convert outer VLAN to ASCII */
-		i = u16_to_ascii(&option.circuit_id, i, outer_vlan);
-		if (i < 0) {
-			return -1;
-		}
+	vlan_offset = u16_to_ascii(&buf, vlan_offset, outer_vlan);
+	if (vlan_offset < 0)
+		return vlan_offset;
+	buf.name[--vlan_offset] = '.';
 
-	}
+	len = copy_dev_name(&option.circuit_id, 0, dev, 0);
+	if (len < 0)
+		return len;
 
-	/* Insert device name and left-align circuit ID */
-	i = copy_dev_name(&option.circuit_id, i, &dev);
-	if (i < 0)
-		return -1;
+	len = copy_dev_name(&option.circuit_id, len, &buf, vlan_offset);
+	if (len < 0)
+		return len;
 
-	return xdp_store_bytes(ctx, offset, &option, sizeof (option), 0);
+	return xdp_store_bytes(ctx, pkt_offset, &option, sizeof(option), 0);
 }
 
 /* Inserts DHCP option 255 into the received dhcp packet
@@ -383,7 +313,6 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 		goto out;
 
 	memcpy(dev.name, dev_config, RAI_OPTION_LEN);
-	dev.len = str_len(&dev);
 
 	/* Increment offset by 4 bytes for each VLAN (to accomodate VLAN headers */
 #pragma unroll VLAN_MAX_DEPTH
@@ -614,7 +543,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 			bpf_printk("Going to write DHCP option 82 at offset %i", option_offset);
 
 			/* Insert Option 82 before END option */
-			if (write_dhcp_option_82(ctx, option_offset, &vlans, dev)) {
+			if (write_dhcp_option_82(ctx, option_offset, &vlans, &dev)) {
 				bpf_printk("Could not write DHCP option 82 at offset %i", option_offset);
 				//return XDP_ABORTED;
 				break;

From b970472bc6be8036b429a4d3835ff55b0c6b15b5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Sat, 13 Nov 2021 00:05:48 +0100
Subject: [PATCH 6/7] dhcp_user_xdp: Fix indentation of switch cases
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The case statements of the option parsing 'switch' had grown an extra level
of indentation. Get rid of that.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 dhcp-relay/dhcp_user_xdp.c | 92 +++++++++++++++++++-------------------
 1 file changed, 46 insertions(+), 46 deletions(-)

diff --git a/dhcp-relay/dhcp_user_xdp.c b/dhcp-relay/dhcp_user_xdp.c
index a2ea5e5..803e55e 100644
--- a/dhcp-relay/dhcp_user_xdp.c
+++ b/dhcp-relay/dhcp_user_xdp.c
@@ -113,54 +113,54 @@ int main(int argc, char **argv) {
 	unsigned char *mac;
 	struct ifreq ifr;
 
-	while ((opt = getopt_long(argc, argv, "hui:d:m:s:", options, NULL)) !=
-		-1) {
+	while ((opt = getopt_long(argc, argv, "hui:d:m:s:", options, NULL)) != -1) {
 		switch (opt) {
-			case 'i':	/* Physical interface */
-				strncpy(dev, optarg, IF_NAMESIZE);
-				dev[IF_NAMESIZE - 1] = '\0';
-				ifindex = if_nametoindex(dev);
-				if (ifindex <= 0) {
-					printf("Couldn't find ifname:%s \n", dev);
-					return -EINVAL;
-				}
-				break;
-			case 'd':	/* DHCP server address */
-				if (inet_aton(optarg, &dhcp_server_addr) == 0) {
-					fprintf(stderr,
-						"Couldn't validate DHCP server IP address:%s\n",
-						optarg);
-					return -EINVAL;
-				}
-				dhcp_server_addr_set = true;
-				break;
-			case 's':	/* Relay agent address */
-				if (inet_aton(optarg, &relay_agent_addr) == 0) {
-					fprintf(stderr,
-						"Couldn't validate relay agent IP address:%s\n",
-						optarg);
-					return -EINVAL;
-				}
-				relay_agent_addr_set = true;
-				break;
-			case 'm':	/* Mode: skb or native */
-				if (strcmp(optarg, "skb") == 0) {
-					xdp_flags = XDP_FLAGS_SKB_MODE;
-				} else if (strcmp(optarg, "drv") != 0) {
-					fprintf(stderr, "Invalid mode: %s\n", optarg);
-					return -EINVAL;
-				}
-
-				break;
-			case 'u':	/* Unload XDP program */
-				do_unload = 1;
-				break;
-			case 'h':	/* Help menu */
-				print_usage(argv);
-				exit(0);
-			default:
-				fprintf(stderr, "Unknown option %s\n", argv[optind]);
+		case 'i':	/* Physical interface */
+			strncpy(dev, optarg, IF_NAMESIZE);
+			dev[IF_NAMESIZE - 1] = '\0';
+			ifindex = if_nametoindex(dev);
+			if (ifindex <= 0) {
+				printf("Couldn't find ifname:%s \n", dev);
+				return -EINVAL;
+			}
+			break;
+		case 'd':	/* DHCP server address */
+			if (inet_aton(optarg, &dhcp_server_addr) == 0) {
+				fprintf(stderr,
+					"Couldn't validate DHCP server IP address:%s\n",
+					optarg);
+				return -EINVAL;
+			}
+			dhcp_server_addr_set = true;
+			break;
+		case 's':	/* Relay agent address */
+			if (inet_aton(optarg, &relay_agent_addr) == 0) {
+				fprintf(stderr,
+					"Couldn't validate relay agent IP address:%s\n",
+					optarg);
+				return -EINVAL;
+			}
+			relay_agent_addr_set = true;
+			break;
+		case 'm':	/* Mode: skb or native */
+			if (strcmp(optarg, "skb") == 0) {
+				xdp_flags = XDP_FLAGS_SKB_MODE;
+			} else if (strcmp(optarg, "drv") != 0) {
+				fprintf(stderr, "Invalid mode: %s\n", optarg);
 				return -EINVAL;
+			}
+
+			break;
+		case 'u':	/* Unload XDP program */
+			do_unload = 1;
+			break;
+
+		case 'h':	/* Help menu */
+			print_usage(argv);
+			exit(0);
+		default:
+			fprintf(stderr, "Unknown option %s\n", argv[optind]);
+			return -EINVAL;
 		}
 	}
 

From fd2b7509805e2308c2b0ba01f677b7257ad09227 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Sat, 13 Nov 2021 00:07:30 +0100
Subject: [PATCH 7/7] dhcp_user_xdp: Add -v option to enable verbose logging
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Add a -v option to turn on verbose logging in libbpf; this makes it
possible to see which relocations libbpf is making, which is useful to see
which functions get turned into separate sub functions.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 dhcp-relay/dhcp_user_xdp.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/dhcp-relay/dhcp_user_xdp.c b/dhcp-relay/dhcp_user_xdp.c
index 803e55e..3ba4dc7 100644
--- a/dhcp-relay/dhcp_user_xdp.c
+++ b/dhcp-relay/dhcp_user_xdp.c
@@ -28,6 +28,7 @@ static const struct option options[] = {
 	{ "relay-agent-address", required_argument, NULL, 's'},
 	{ "mode", required_argument, NULL, 'm'},
 	{ "unload", no_argument, NULL, 'u'},
+	{ "verbose", no_argument, NULL, 'v'},
 	{ 0, 0, NULL, 0}
 };
 
@@ -89,6 +90,13 @@ int xdp_link_attach(int ifindex, __u32 xdp_flags, int prog_fd) {
 	return 0;
 }
 
+static int libbpf_print_func(enum libbpf_print_level level, const char *format,
+			     va_list args)
+{
+	return vfprintf(stderr, format, args);
+}
+
+
 int main(int argc, char **argv) {
 
 	char filename[256] = "dhcp_kern_xdp.o";
@@ -113,7 +121,7 @@ int main(int argc, char **argv) {
 	unsigned char *mac;
 	struct ifreq ifr;
 
-	while ((opt = getopt_long(argc, argv, "hui:d:m:s:", options, NULL)) != -1) {
+	while ((opt = getopt_long(argc, argv, "huvi:d:m:s:", options, NULL)) != -1) {
 		switch (opt) {
 		case 'i':	/* Physical interface */
 			strncpy(dev, optarg, IF_NAMESIZE);
@@ -155,6 +163,10 @@ int main(int argc, char **argv) {
 			do_unload = 1;
 			break;
 
+		case 'v':	/* Verbose libbpf logging */
+			libbpf_set_print(libbpf_print_func);
+			break;
+
 		case 'h':	/* Help menu */
 			print_usage(argv);
 			exit(0);