net: Export IGMP/MLD message validation code

With this patch, the IGMP and MLD message validation functions are moved
from the bridge code to IPv4/IPv6 multicast files. Some small
refactoring was done to enhance readibility and to iron out some
differences in behaviour between the IGMP and MLD parsing code (e.g. the
skb-cloning of MLD messages is now only done if necessary, just like the
IGMP part always did).

Finally, these IGMP and MLD message validation functions are exported so
that not only the bridge can use it but batman-adv later, too.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 30 insertions, 188 deletions

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index b52f4cb8aee9..2d69d5cab52f 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -975,9 +975,6 @@ static int br_ip4_multicast_igmp3_report(struct net_bridge *br,
 	int err = 0;
 	__be32 group;
 
-	if (!pskb_may_pull(skb, sizeof(*ih)))
-		return -EINVAL;
-
 	ih = igmpv3_report_hdr(skb);
 	num = ntohs(ih->ngrec);
 	len = sizeof(*ih);
@@ -1248,25 +1245,14 @@ static int br_ip4_multicast_query(struct net_bridge *br,
 			max_delay = 10 * HZ;
 			group = 0;
 		}
-	} else {
-		if (!pskb_may_pull(skb, sizeof(struct igmpv3_query))) {
-			err = -EINVAL;
-			goto out;
-		}
-
+	} else if (skb->len >= sizeof(*ih3)) {
 		ih3 = igmpv3_query_hdr(skb);
 		if (ih3->nsrcs)
 			goto out;
 
 		max_delay = ih3->code ?
 			    IGMPV3_MRC(ih3->code) * (HZ / IGMP_TIMER_SCALE) : 1;
-	}
-
-	/* RFC2236+RFC3376 (IGMPv2+IGMPv3) require the multicast link layer
-	 * all-systems destination addresses (224.0.0.1) for general queries
-	 */
-	if (!group && iph->daddr != htonl(INADDR_ALLHOSTS_GROUP)) {
-		err = -EINVAL;
+	} else {
 		goto out;
 	}
 
@@ -1329,12 +1315,6 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 	    (port && port->state == BR_STATE_DISABLED))
 		goto out;
 
-	/* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */
-	if (!(ipv6_addr_type(&ip6h->saddr) & IPV6_ADDR_LINKLOCAL)) {
-		err = -EINVAL;
-		goto out;
-	}
-
 	if (skb->len == sizeof(*mld)) {
 		if (!pskb_may_pull(skb, sizeof(*mld))) {
 			err = -EINVAL;
@@ -1358,14 +1338,6 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 
 	is_general_query = group && ipv6_addr_any(group);
 
-	/* RFC2710+RFC3810 (MLDv1+MLDv2) require the multicast link layer
-	 * all-nodes destination address (ff02::1) for general queries
-	 */
-	if (is_general_query && !ipv6_addr_is_ll_all_nodes(&ip6h->daddr)) {
-		err = -EINVAL;
-		goto out;
-	}
-
 	if (is_general_query) {
 		saddr.proto = htons(ETH_P_IPV6);
 		saddr.u.ip6 = ip6h->saddr;
@@ -1557,66 +1529,22 @@ static int br_multicast_ipv4_rcv(struct net_bridge *br,
 				 struct sk_buff *skb,
 				 u16 vid)
 {
-	struct sk_buff *skb2 = skb;
-	const struct iphdr *iph;
+	struct sk_buff *skb_trimmed = NULL;
 	struct igmphdr *ih;
-	unsigned int len;
-	unsigned int offset;
 	int err;
 
-	/* We treat OOM as packet loss for now. */
-	if (!pskb_may_pull(skb, sizeof(*iph)))
-		return -EINVAL;
-
-	iph = ip_hdr(skb);
-
-	if (iph->ihl < 5 || iph->version != 4)
-		return -EINVAL;
-
-	if (!pskb_may_pull(skb, ip_hdrlen(skb)))
-		return -EINVAL;
-
-	iph = ip_hdr(skb);
+	err = ip_mc_check_igmp(skb, &skb_trimmed);
 
-	if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
-		return -EINVAL;
-
-	if (iph->protocol != IPPROTO_IGMP) {
-		if (!ipv4_is_local_multicast(iph->daddr))
+	if (err == -ENOMSG) {
+		if (!ipv4_is_local_multicast(ip_hdr(skb)->daddr))
 			BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
 		return 0;
+	} else if (err < 0) {
+		return err;
 	}
 
-	len = ntohs(iph->tot_len);
-	if (skb->len < len || len < ip_hdrlen(skb))
-		return -EINVAL;
-
-	if (skb->len > len) {
-		skb2 = skb_clone(skb, GFP_ATOMIC);
-		if (!skb2)
-			return -ENOMEM;
-
-		err = pskb_trim_rcsum(skb2, len);
-		if (err)
-			goto err_out;
-	}
-
-	len -= ip_hdrlen(skb2);
-	offset = skb_network_offset(skb2) + ip_hdrlen(skb2);
-	__skb_pull(skb2, offset);
-	skb_reset_transport_header(skb2);
-
-	err = -EINVAL;
-	if (!pskb_may_pull(skb2, sizeof(*ih)))
-		goto out;
-
-	if (skb_checksum_simple_validate(skb2))
-		goto out;
-
-	err = 0;
-
 	BR_INPUT_SKB_CB(skb)->igmp = 1;
-	ih = igmp_hdr(skb2);
+	ih = igmp_hdr(skb);
 
 	switch (ih->type) {
 	case IGMP_HOST_MEMBERSHIP_REPORT:
@@ -1625,21 +1553,19 @@ static int br_multicast_ipv4_rcv(struct net_bridge *br,
 		err = br_ip4_multicast_add_group(br, port, ih->group, vid);
 		break;
 	case IGMPV3_HOST_MEMBERSHIP_REPORT:
-		err = br_ip4_multicast_igmp3_report(br, port, skb2, vid);
+		err = br_ip4_multicast_igmp3_report(br, port, skb_trimmed, vid);
 		break;
 	case IGMP_HOST_MEMBERSHIP_QUERY:
-		err = br_ip4_multicast_query(br, port, skb2, vid);
+		err = br_ip4_multicast_query(br, port, skb_trimmed, vid);
 		break;
 	case IGMP_HOST_LEAVE_MESSAGE:
 		br_ip4_multicast_leave_group(br, port, ih->group, vid);
 		break;
 	}
 
-out:
-	__skb_push(skb2, offset);
-err_out:
-	if (skb2 != skb)
-		kfree_skb(skb2);
+	if (skb_trimmed)
+		kfree_skb(skb_trimmed);
+
 	return err;
 }
 
@@ -1649,126 +1575,42 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
 				 struct sk_buff *skb,
 				 u16 vid)
 {
-	struct sk_buff *skb2;
-	const struct ipv6hdr *ip6h;
-	u8 icmp6_type;
-	u8 nexthdr;
-	__be16 frag_off;
-	unsigned int len;
-	int offset;
+	struct sk_buff *skb_trimmed = NULL;
+	struct mld_msg *mld;
 	int err;
 
-	if (!pskb_may_pull(skb, sizeof(*ip6h)))
-		return -EINVAL;
+	err = ipv6_mc_check_mld(skb, &skb_trimmed);
 
-	ip6h = ipv6_hdr(skb);
-
-	/*
-	 * We're interested in MLD messages only.
-	 *  - Version is 6
-	 *  - MLD has always Router Alert hop-by-hop option
-	 *  - But we do not support jumbrograms.
-	 */
-	if (ip6h->version != 6)
-		return 0;
-
-	/* Prevent flooding this packet if there is no listener present */
-	if (!ipv6_addr_is_ll_all_nodes(&ip6h->daddr))
-		BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
-
-	if (ip6h->nexthdr != IPPROTO_HOPOPTS ||
-	    ip6h->payload_len == 0)
-		return 0;
-
-	len = ntohs(ip6h->payload_len) + sizeof(*ip6h);
-	if (skb->len < len)
-		return -EINVAL;
-
-	nexthdr = ip6h->nexthdr;
-	offset = ipv6_skip_exthdr(skb, sizeof(*ip6h), &nexthdr, &frag_off);
-
-	if (offset < 0 || nexthdr != IPPROTO_ICMPV6)
+	if (err == -ENOMSG) {
+		if (!ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr))
+			BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
 		return 0;
-
-	/* Okay, we found ICMPv6 header */
-	skb2 = skb_clone(skb, GFP_ATOMIC);
-	if (!skb2)
-		return -ENOMEM;
-
-	err = -EINVAL;
-	if (!pskb_may_pull(skb2, offset + sizeof(struct icmp6hdr)))
-		goto out;
-
-	len -= offset - skb_network_offset(skb2);
-
-	__skb_pull(skb2, offset);
-	skb_reset_transport_header(skb2);
-	skb_postpull_rcsum(skb2, skb_network_header(skb2),
-			   skb_network_header_len(skb2));
-
-	icmp6_type = icmp6_hdr(skb2)->icmp6_type;
-
-	switch (icmp6_type) {
-	case ICMPV6_MGM_QUERY:
-	case ICMPV6_MGM_REPORT:
-	case ICMPV6_MGM_REDUCTION:
-	case ICMPV6_MLD2_REPORT:
-		break;
-	default:
-		err = 0;
-		goto out;
-	}
-
-	/* Okay, we found MLD message. Check further. */
-	if (skb2->len > len) {
-		err = pskb_trim_rcsum(skb2, len);
-		if (err)
-			goto out;
-		err = -EINVAL;
+	} else if (err < 0) {
+		return err;
 	}
 
-	ip6h = ipv6_hdr(skb2);
-
-	if (skb_checksum_validate(skb2, IPPROTO_ICMPV6, ip6_compute_pseudo))
-		goto out;
-
-	err = 0;
-
 	BR_INPUT_SKB_CB(skb)->igmp = 1;
+	mld = (struct mld_msg *)skb_transport_header(skb);
 
-	switch (icmp6_type) {
+	switch (mld->mld_type) {
 	case ICMPV6_MGM_REPORT:
-	    {
-		struct mld_msg *mld;
-		if (!pskb_may_pull(skb2, sizeof(*mld))) {
-			err = -EINVAL;
-			goto out;
-		}
-		mld = (struct mld_msg *)skb_transport_header(skb2);
 		BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
 		err = br_ip6_multicast_add_group(br, port, &mld->mld_mca, vid);
 		break;
-	    }
 	case ICMPV6_MLD2_REPORT:
-		err = br_ip6_multicast_mld2_report(br, port, skb2, vid);
+		err = br_ip6_multicast_mld2_report(br, port, skb_trimmed, vid);
 		break;
 	case ICMPV6_MGM_QUERY:
-		err = br_ip6_multicast_query(br, port, skb2, vid);
+		err = br_ip6_multicast_query(br, port, skb_trimmed, vid);
 		break;
 	case ICMPV6_MGM_REDUCTION:
-	    {
-		struct mld_msg *mld;
-		if (!pskb_may_pull(skb2, sizeof(*mld))) {
-			err = -EINVAL;
-			goto out;
-		}
-		mld = (struct mld_msg *)skb_transport_header(skb2);
 		br_ip6_multicast_leave_group(br, port, &mld->mld_mca, vid);
-	    }
+		break;
 	}
 
-out:
-	kfree_skb(skb2);
+	if (skb_trimmed)
+		kfree_skb(skb_trimmed);
+
 	return err;
 }
 #endif