[PATCH] netfilter: fix regression in looped (broad|multi)cast's MAC handing

[PATCH] netfilter: fix regression in looped (broad|multi)cast's MAC handing

[Ignacy Gawędzki]

In 5648b5e1169f, the test for non-empty MAC header introduced in
2c38de4c1f8da7 has been replaced with a test for a set MAC header,
which breaks the case when the MAC header has been reset (using
skb_reset_mac_header), as is the case with looped-back multicast
packets.

This patch adds a test for a non-empty MAC header in addition to the
test for a set MAC header.  The same two tests are also implemented in
nfnetlink_log.c, where the initial code of 2c38de4c1f8da7 has not been
touched, but where supposedly the same situation may happen.

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
---
 net/netfilter/nfnetlink_log.c   | 3 ++-
 net/netfilter/nfnetlink_queue.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 691ef4cffdd9..7f83f9697fc1 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -556,7 +556,8 @@ __build_packet_message(struct nfnl_log_net *log,
 		goto nla_put_failure;
 
 	if (indev && skb->dev &&
-	    skb->mac_header != skb->network_header) {
+	    skb_mac_header_was_set(skb) &&
+	    skb_mac_header_len(skb) != 0) {
 		struct nfulnl_msg_packet_hw phw;
 		int len;
 
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 4acc4b8e9fe5..959527708e38 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -560,7 +560,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 		goto nla_put_failure;
 
 	if (indev && entskb->dev &&
-	    skb_mac_header_was_set(entskb)) {
+	    skb_mac_header_was_set(entskb) &&
+	    skb_mac_header_len(entskb) != 0) {
 		struct nfqnl_msg_packet_hw phw;
 		int len;
 
-- 
2.32.0

Re: [PATCH] netfilter: fix regression in looped (broad|multi)cast's MAC handing

[Denis Kirjanov]

12/10/21 3:26 PM, Ignacy Gawędzki пишет:
> In 5648b5e1169f, the test for non-empty MAC header introduced in
> 2c38de4c1f8da7 has been replaced with a test for a set MAC header,
> which breaks the case when the MAC header has been reset (using
> skb_reset_mac_header), as is the case with looped-back multicast
> packets.
> 
> This patch adds a test for a non-empty MAC header in addition to the
> test for a set MAC header.  The same two tests are also implemented in
> nfnetlink_log.c, where the initial code of 2c38de4c1f8da7 has not been
> touched, but where supposedly the same situation may happen.
>
Fixes: 2c38de4c1f8da7 ("netfilter: fix looped (broad|multi)cast's MAC 
handling")

> Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
> ---
>   net/netfilter/nfnetlink_log.c   | 3 ++-
>   net/netfilter/nfnetlink_queue.c | 3 ++-
>   2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
> index 691ef4cffdd9..7f83f9697fc1 100644
> --- a/net/netfilter/nfnetlink_log.c
> +++ b/net/netfilter/nfnetlink_log.c
> @@ -556,7 +556,8 @@ __build_packet_message(struct nfnl_log_net *log,
>   		goto nla_put_failure;
>   
>   	if (indev && skb->dev &&
> -	    skb->mac_header != skb->network_header) {
> +	    skb_mac_header_was_set(skb) &&
> +	    skb_mac_header_len(skb) != 0) {
>   		struct nfulnl_msg_packet_hw phw;
>   		int len;
>   
> diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
> index 4acc4b8e9fe5..959527708e38 100644
> --- a/net/netfilter/nfnetlink_queue.c
> +++ b/net/netfilter/nfnetlink_queue.c
> @@ -560,7 +560,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
>   		goto nla_put_failure;
>   
>   	if (indev && entskb->dev &&
> -	    skb_mac_header_was_set(entskb)) {
> +	    skb_mac_header_was_set(entskb) &&
> +	    skb_mac_header_len(entskb) != 0) {
>   		struct nfqnl_msg_packet_hw phw;
>   		int len;
>   
>