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 d...@openvswtich.org. The second version can be found at: http://www.mail-archive.com/dev@openvswitch.org/msg09001.html It needs to be updated to call tcp_encap_enable() Cc: Eric Dumazet <eric.duma...@gmail.com> Signed-off-by: Simon Horman <ho...@verge.net.au> --- v4 * Make use of static_key, a tonic for insanity suggested by Eric Dumazet v3 * 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. --- include/linux/tcp.h | 3 +++ include/net/tcp.h | 1 + net/ipv4/tcp_ipv4.c | 34 +++++++++++++++++++++++++++++++++- 3 files changed, 37 insertions(+), 1 deletion(-) 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/include/net/tcp.h b/include/net/tcp.h index d5984e3..35d4070 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1576,5 +1576,6 @@ static inline struct tcp_extend_values *tcp_xv(struct request_values *rvp) extern void tcp_v4_init(void); extern void tcp_init(void); +extern void tcp_encap_enable(void); #endif /* _TCP_H */ diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 0cb86ce..907735d 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -62,6 +62,7 @@ #include <linux/init.h> #include <linux/times.h> #include <linux/slab.h> +#include <linux/static_key.h> #include <net/net_namespace.h> #include <net/icmp.h> @@ -1657,6 +1658,14 @@ csum_err: } EXPORT_SYMBOL(tcp_v4_do_rcv); +static struct static_key tcp_encap_needed __read_mostly; +void tcp_encap_enable(void) +{ + if (!static_key_enabled(&tcp_encap_needed)) + static_key_slow_inc(&tcp_encap_needed); +} +EXPORT_SYMBOL(tcp_encap_enable); + /* * From tcp_input.c */ @@ -1666,6 +1675,7 @@ 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); @@ -1726,9 +1736,30 @@ process: bh_lock_sock_nested(sk); ret = 0; + + tp = tcp_sk(sk); + if (static_key_false(&tcp_encap_needed)) { + int (*encap_rcv)(struct sock *sk, struct sk_buff *skb); + 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 = net_dma_find_channel(); if (tp->ucopy.dma_chan) @@ -1744,6 +1775,7 @@ 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 dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
