diff options
| author | Eyal Birger | 2015-03-01 14:58:31 +0200 |
|---|---|---|
| committer | David S. Miller | 2015-03-02 00:19:30 -0500 |
| commit | 744d5a3e9fe2690dd85d9991dbb078301694658b (patch) | |
| tree | e8e54af77636cf51a1146cd638275f940bfe3db9 /include/net | |
| parent | 3bc3b96f3b455bd14a8ccd83ffffc85625aba641 (diff) | |
net: move skb->dropcount to skb->cb[]
Commit 977750076d98 ("af_packet: add interframe drop cmsg (v6)")
unionized skb->mark and skb->dropcount in order to allow recording
of the socket drop count while maintaining struct sk_buff size.
skb->dropcount was introduced since there was no available room
in skb->cb[] in packet sockets. However, its introduction led to
the inability to export skb->mark, or any other aliased field to
userspace if so desired.
Moving the dropcount metric to skb->cb[] eliminates this problem
at the expense of 4 bytes less in skb->cb[] for protocol families
using it.
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net')
| -rw-r--r-- | include/net/sock.h | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/include/net/sock.h b/include/net/sock.h index 0996fe451e5f..38369d3580a1 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2078,13 +2078,27 @@ static inline int sock_intr_errno(long timeo) return timeo == MAX_SCHEDULE_TIMEOUT ? -ERESTARTSYS : -EINTR; } +struct sock_skb_cb { + u32 dropcount; +}; + +/* Store sock_skb_cb at the end of skb->cb[] so protocol families + * using skb->cb[] would keep using it directly and utilize its + * alignement guarantee. + */ +#define SOCK_SKB_CB_OFFSET ((FIELD_SIZEOF(struct sk_buff, cb) - \ + sizeof(struct sock_skb_cb))) + +#define SOCK_SKB_CB(__skb) ((struct sock_skb_cb *)((__skb)->cb + \ + SOCK_SKB_CB_OFFSET)) + #define sock_skb_cb_check_size(size) \ - BUILD_BUG_ON((size) > FIELD_SIZEOF(struct sk_buff, cb)) + BUILD_BUG_ON((size) > SOCK_SKB_CB_OFFSET) static inline void sock_skb_set_dropcount(const struct sock *sk, struct sk_buff *skb) { - skb->dropcount = atomic_read(&sk->sk_drops); + SOCK_SKB_CB(skb)->dropcount = atomic_read(&sk->sk_drops); } void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk, |