net: tcp: Avoid directly accessing address of unaligned struct

Use UNALIGNED_MEMBER_ADDR when getting the address of possibly
unaligned structures members instead of attempting to directly
get the address as an offset.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

Author: aescolar

subsys/net/ip/tcp.c

@@ -1262,20 +1262,20 @@ static int tcp_header_add(struct tcp *conn, struct net_pkt *pkt, uint8_t flags,
 
 	memset(th, 0, sizeof(struct tcphdr));
 
-	UNALIGNED_PUT(conn->src.sin.sin_port, &th->th_sport);
-	UNALIGNED_PUT(conn->dst.sin.sin_port, &th->th_dport);
+	UNALIGNED_PUT(conn->src.sin.sin_port, UNALIGNED_MEMBER_ADDR(th, th_sport));
+	UNALIGNED_PUT(conn->dst.sin.sin_port, UNALIGNED_MEMBER_ADDR(th, th_dport));
 	th->th_off = 5;
 
 	if (conn->send_options.mss_found) {
 		th->th_off++;
 	}
 
 	UNALIGNED_PUT(flags, &th->th_flags);
-	UNALIGNED_PUT(htons(conn->recv_win), &th->th_win);
-	UNALIGNED_PUT(htonl(seq), &th->th_seq);
+	UNALIGNED_PUT(htons(conn->recv_win), UNALIGNED_MEMBER_ADDR(th, th_win));
+	UNALIGNED_PUT(htonl(seq), UNALIGNED_MEMBER_ADDR(th, th_seq));
 
 	if (ACK & flags) {
-		UNALIGNED_PUT(htonl(conn->ack), &th->th_ack);
+		UNALIGNED_PUT(htonl(conn->ack), UNALIGNED_MEMBER_ADDR(th, th_ack));
 	}
 
 	return net_pkt_set_data(pkt, &tcp_access);
@@ -1415,13 +1415,13 @@ void net_tcp_reply_rst(struct net_pkt *pkt)
 
 	memset(th_rst, 0, sizeof(struct tcphdr));
 
-	UNALIGNED_PUT(th_pkt->th_dport, &th_rst->th_sport);
-	UNALIGNED_PUT(th_pkt->th_sport, &th_rst->th_dport);
+	UNALIGNED_PUT(th_pkt->th_dport, UNALIGNED_MEMBER_ADDR(th_rst, th_sport));
+	UNALIGNED_PUT(th_pkt->th_sport, UNALIGNED_MEMBER_ADDR(th_rst, th_dport));
 	th_rst->th_off = 5;
 
 	if (th_flags(th_pkt) & ACK) {
 		UNALIGNED_PUT(RST, &th_rst->th_flags);
-		UNALIGNED_PUT(th_pkt->th_ack, &th_rst->th_seq);
+		UNALIGNED_PUT(th_pkt->th_ack, UNALIGNED_MEMBER_ADDR(th_rst, th_seq));
 	} else {
 		uint32_t ack = ntohl(th_pkt->th_seq) + tcp_data_len(pkt);
 
@@ -1430,7 +1430,7 @@ void net_tcp_reply_rst(struct net_pkt *pkt)
 		}
 
 		UNALIGNED_PUT(RST | ACK, &th_rst->th_flags);
-		UNALIGNED_PUT(htonl(ack), &th_rst->th_ack);
+		UNALIGNED_PUT(htonl(ack), UNALIGNED_MEMBER_ADDR(th_rst, th_ack));
 	}
 
 	ret = net_pkt_set_data(rst, &tcp_access_rst);

subsys/net/ip/tcp_private.h

@@ -6,20 +6,22 @@
  */
 
 #include "tp.h"
+#include <zephyr/toolchain/gcc.h>
 
 #define is(_a, _b) (strcmp((_a), (_b)) == 0)
 
 #ifndef MIN3
 #define MIN3(_a, _b, _c) MIN((_a), MIN((_b), (_c)))
 #endif
 
-#define th_sport(_x) UNALIGNED_GET(&(_x)->th_sport)
-#define th_dport(_x) UNALIGNED_GET(&(_x)->th_dport)
-#define th_seq(_x) ntohl(UNALIGNED_GET(&(_x)->th_seq))
-#define th_ack(_x) ntohl(UNALIGNED_GET(&(_x)->th_ack))
+#define th_sport(_x) UNALIGNED_GET(UNALIGNED_MEMBER_ADDR((_x), th_sport))
+#define th_dport(_x) UNALIGNED_GET(UNALIGNED_MEMBER_ADDR((_x), th_dport))
+#define th_seq(_x) ntohl(UNALIGNED_GET(UNALIGNED_MEMBER_ADDR((_x), th_seq)))
+#define th_ack(_x) ntohl(UNALIGNED_GET(UNALIGNED_MEMBER_ADDR((_x), th_ack)))
+
 #define th_off(_x) ((_x)->th_off)
-#define th_flags(_x) UNALIGNED_GET(&(_x)->th_flags)
-#define th_win(_x) UNALIGNED_GET(&(_x)->th_win)
+#define th_flags(_x) UNALIGNED_GET(UNALIGNED_MEMBER_ADDR((_x), th_flags))
+#define th_win(_x) UNALIGNED_GET(UNALIGNED_MEMBER_ADDR((_x), th_win))
 
 #define tcp_slist(_conn, _slist, _op, _type, _link)			\
 ({									\