net: ip: igmp: Fix wrong header length

The header length of the net ip packet was calculated using only the
net_pkt_ip_hdr_len function. The correct header length should be
calculated by adding net_pkt_ip_hdr_len and net_pkt_ipv4_opts_len. This
resulted in an incorrect IGMP version type in case of IGMPv2 message
(when IGMPv3 was enabled). The IGMP message was not parsed correctly and
therefore dropped.

Signed-off-by: Ibe Van de Veire <ibe.vandeveire@basalte.be>

Author: IVandeVeire

subsys/net/ip/igmp.c

@@ -424,7 +424,8 @@ enum net_verdict net_ipv4_igmp_input(struct net_pkt *pkt, struct net_ipv4_hdr *i
 	struct net_ipv4_igmp_v2_query *igmpv2_hdr;
 	enum igmp_version version;
 	int ret;
-	int igmp_buf_len = pkt->buffer->len - net_pkt_ip_hdr_len(pkt);
+	int igmp_buf_len =
+		pkt->buffer->len - (net_pkt_ip_hdr_len(pkt) + net_pkt_ipv4_opts_len(pkt));
 
 	/* Detect IGMP type (RFC 3376 ch 7.1) */
 	if (igmp_buf_len == 8) {