netfilter: fix looped (broad|multi)cast's MAC handling

By default, when broadcast or multicast packet are sent from a local
application, they are sent to the interface then looped by the kernel
to other local applications, going throught netfilter hooks in the
process.

These looped packet have their MAC header removed from the skb by the
kernel looping code. This confuse various netfilter's netlink queue,
netlink log and the legacy ip_queue, because they try to extract a
hardware address from these packets, but extracts a part of the IP
header instead.

This patch prevent NFQUEUE, NFLOG and ip_QUEUE to include a MAC header
if there is none in the packet.

Signed-off-by: Nicolas Cavallari <cavallar@lri.fr>
Signed-off-by: Patrick McHardy <kaber@trash.net>

4 files changed, 8 insertions, 4 deletions

diff --git a/net/ipv4/netfilter/ip_queue.c b/net/ipv4/netfilter/ip_queue.c
index f7f9bd7ba12d..5c9b9d963918 100644
--- a/net/ipv4/netfilter/ip_queue.c
+++ b/net/ipv4/netfilter/ip_queue.c
@@ -203,7 +203,8 @@ ipq_build_packet_message(struct nf_queue_entry *entry, int *errp)
         else
                 pmsg->outdev_name[0] = '\0';
 
-        if (entry->indev && entry->skb->dev) {
+        if (entry->indev && entry->skb->dev &&
+            entry->skb->mac_header != entry->skb->network_header) {
                 pmsg->hw_type = entry->skb->dev->type;
                 pmsg->hw_addrlen = dev_parse_header(entry->skb,
                                                     pmsg->hw_addr);
diff --git a/net/ipv6/netfilter/ip6_queue.c b/net/ipv6/netfilter/ip6_queue.c
index 065fe405fb58..249394863284 100644
--- a/net/ipv6/netfilter/ip6_queue.c
+++ b/net/ipv6/netfilter/ip6_queue.c
@@ -204,7 +204,8 @@ ipq_build_packet_message(struct nf_queue_entry *entry, int *errp)
         else
                 pmsg->outdev_name[0] = '\0';
 
-        if (entry->indev && entry->skb->dev) {
+        if (entry->indev && entry->skb->dev &&
+            entry->skb->mac_header != entry->skb->network_header) {
                 pmsg->hw_type = entry->skb->dev->type;
                 pmsg->hw_addrlen = dev_parse_header(entry->skb, pmsg->hw_addr);
         }
diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index e0ee010935e7..2e7ccbb43ddb 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -456,7 +456,8 @@ __build_packet_message(struct nfulnl_instance *inst,
         if (skb->mark)
                 NLA_PUT_BE32(inst->skb, NFULA_MARK, htonl(skb->mark));
 
-        if (indev && skb->dev) {
+        if (indev && skb->dev &&
+            skb->mac_header != skb->network_header) {
                 struct nfulnl_msg_packet_hw phw;
                 int len = dev_parse_header(skb, phw.hw_addr);
                 if (len > 0) {
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index b83123f12b42..fdd2fafe0a14 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -335,7 +335,8 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue,
         if (entskb->mark)
                 NLA_PUT_BE32(skb, NFQA_MARK, htonl(entskb->mark));
 
-        if (indev && entskb->dev) {
+        if (indev && entskb->dev &&
+            entskb->mac_header != entskb->network_header) {
                 struct nfqnl_msg_packet_hw phw;
                 int len = dev_parse_header(entskb, phw.hw_addr);
                 if (len) {