net: lib: dhcpv4: Skip leftover hostname or domain name bytes

When reading and printing hosname or domain name from DHCP options, we need
to skip the leftover bytes that do not fit into the provided buffers.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

Author: pdgendt

subsys/net/lib/dhcpv4/dhcpv4.c

@@ -1081,14 +1081,16 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
 		}
 		case DHCPV4_OPTIONS_HOST_NAME: {
 			char hostname[NET_HOSTNAME_SIZE] = { 0 };
+			uint8_t read_len;
 
 			if (length < 1) {
 				NET_ERR("options_host_name, bad length");
 				return false;
 			}
 
-			if (net_pkt_read(pkt, hostname, MIN(length,
-							    sizeof(hostname) - 1))) {
+			read_len = MIN(length, sizeof(hostname) - 1);
+			if (net_pkt_read(pkt, hostname, read_len) ||
+			    net_pkt_skip(pkt, length - read_len)) {
 				NET_ERR("options_host_name, short packet");
 				return false;
 			}
@@ -1099,14 +1101,16 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
 		}
 		case DHCPV4_OPTIONS_DOMAIN_NAME: {
 			char domain_name[NET_HOSTNAME_SIZE] = { 0 };
+			uint8_t read_len;
 
 			if (length < 1) {
 				NET_ERR("options_domain_name, bad length");
 				return false;
 			}
 
-			if (net_pkt_read(pkt, domain_name, MIN(length,
-							       sizeof(domain_name) - 1))) {
+			read_len = MIN(length, sizeof(domain_name) - 1);
+			if (net_pkt_read(pkt, domain_name, read_len) ||
+			    net_pkt_skip(pkt, length - read_len)) {
 				NET_ERR("options_domain_name, short packet");
 				return false;
 			}