This hook is based on a hook of the same name provided by UDP. It provides a way for to receive packets that have a TCP header and treat them in some alternate way.
It is intended to be used by an implementation of the STT tunneling protocol within Open vSwtich's datapath. A prototype of such an implementation has been made. The STT draft is available at http://tools.ietf.org/html/draft-davie-stt-01 My prototype STT implementation has been posted to the [email protected]. The first version can be found at: http://www.mail-archive.com/[email protected]/msg08877.html Signed-off-by: Simon Horman <[email protected]> --- include/linux/tcp.h | 3 +++ net/ipv4/tcp_ipv4.c | 23 ++++++++++++++++++++++- 2 files changed, 25 insertions(+), 1 deletion(-) v3 * First post to netdev * Replace more UDP references with TCP * Move socket accesses to inside socket lock and release lock on return. v2 * Fix comment to refer to TCP rather than UDP * Allow skb to continue traversing the stack if the encap_rcv callback returns a positive value. This is the same behaviour as the UDP hook. diff --git a/include/linux/tcp.h b/include/linux/tcp.h index b6c62d2..7210b23 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -472,6 +472,9 @@ struct tcp_sock { * contains related tcp_cookie_transactions fields. */ struct tcp_cookie_values *cookie_values; + + /* For encapsulation sockets. */ + int (*encap_rcv)(struct sock *sk, struct sk_buff *skb); }; static inline struct tcp_sock *tcp_sk(const struct sock *sk) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 3a25cf7..9898f71 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1666,8 +1666,10 @@ int tcp_v4_rcv(struct sk_buff *skb) const struct iphdr *iph; const struct tcphdr *th; struct sock *sk; + struct tcp_sock *tp; int ret; struct net *net = dev_net(skb->dev); + int (*encap_rcv)(struct sock *sk, struct sk_buff *skb); if (skb->pkt_type != PACKET_HOST) goto discard_it; @@ -1726,9 +1728,27 @@ process: bh_lock_sock_nested(sk); ret = 0; + + tp = tcp_sk(sk); + encap_rcv = ACCESS_ONCE(tp->encap_rcv); + if (encap_rcv != NULL) { + /* + * This is an encapsulation socket so pass the skb to + * the socket's tcp_encap_rcv() hook. Otherwise, just + * fall through and pass this up the TCP socket. + * up->encap_rcv() returns the following value: + * <=0 if skb was successfully passed to the encap + * handler or was discarded by it. + * >0 if skb should be passed on to TCP. + */ + if (encap_rcv(sk, skb) <= 0) { + ret = 0; + goto unlock_sock; + } + } + if (!sock_owned_by_user(sk)) { #ifdef CONFIG_NET_DMA - struct tcp_sock *tp = tcp_sk(sk); if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY); if (tp->ucopy.dma_chan) @@ -1744,6 +1764,7 @@ process: NET_INC_STATS_BH(net, LINUX_MIB_TCPBACKLOGDROP); goto discard_and_relse; } +unlock_sock: bh_unlock_sock(sk); sock_put(sk); -- 1.7.9.5 _______________________________________________ dev mailing list [email protected] http://openvswitch.org/mailman/listinfo/dev
