Commit 1e4033b5 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: skb_reset_mac_len() must check if mac_header was set 



Recent discussions show that skb_reset_mac_len() should be more careful.

We expect the MAC header being set.

If not, clear skb->mac_len and fire a warning for CONFIG_DEBUG_NET=y builds.

If after investigations we find that not having a MAC header was okay,
we can remove the warning.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/netdev/CANn89iJZGH+yEfJxfPWa3Hm7jxb-aeY2Up4HufmLMnVuQXt38A@mail.gmail.com/T/


Cc: En-Wei Wu <en-wei.wu@canonical.com>
Reviewed-by: default avatarJoe Damato <jdamato@fastly.com>
Reviewed-by: default avatarXuan Zhuo <xuanzhuo@linux.alibaba.com>
Link: https://patch.msgid.link/20241105174403.850330-2-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 3545f9b7

include/linux/skbuff.h

+11 −6
Original line number Diff line number Diff line
@@ -2909,10 +2909,20 @@ static inline void skb_reset_inner_headers(struct sk_buff *skb) 
	skb->inner_transport_header = skb->transport_header;

}



static inline int skb_mac_header_was_set(const struct sk_buff *skb)

{

	return skb->mac_header != (typeof(skb->mac_header))~0U;

}



static inline void skb_reset_mac_len(struct sk_buff *skb)

{

	if (!skb_mac_header_was_set(skb)) {

		DEBUG_NET_WARN_ON_ONCE(1);

		skb->mac_len = 0;

	} else {

		skb->mac_len = skb->network_header - skb->mac_header;

	}

}



static inline unsigned char *skb_inner_transport_header(const struct sk_buff

							*skb)
@@ -3014,11 +3024,6 @@ static inline void skb_set_network_header(struct sk_buff *skb, const int offset) 
	skb->network_header += offset;

}



static inline int skb_mac_header_was_set(const struct sk_buff *skb)

{

	return skb->mac_header != (typeof(skb->mac_header))~0U;

}



static inline unsigned char *skb_mac_header(const struct sk_buff *skb)

{

	DEBUG_NET_WARN_ON_ONCE(!skb_mac_header_was_set(skb));