tcp: allow zerocopy with fastopen

Accept MSG_ZEROCOPY in all the TCP states that allow sendmsg. Remove
the explicit check for ESTABLISHED and CLOSE_WAIT states.

This requires correctly handling zerocopy state (uarg, sk_zckey) in
all paths reachable from other TCP states. Such as the EPIPE case
in sk_stream_wait_connect, which a sendmsg() in incorrect state will
now hit. Most paths are already safe.

Only extension needed is for TCP Fastopen active open. This can build
an skb with data in tcp_send_syn_data. Pass the uarg along with other
fastopen state, so that this skb also generates a zerocopy
notification on release.

Tested with active and passive tcp fastopen packetdrill scripts at
https://github.com/wdebruij/packetdrill/commit/1747eef03d25a2404e8132817d0f1244fd6f129d

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6527f61f59ff..26a2948dca95 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3455,6 +3455,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
                         skb_trim(syn_data, copied);
                         space = copied;
                 }
+                skb_zcopy_set(syn_data, fo->uarg, NULL);
         }
         /* No more data pending in inet_wait_for_connect() */
         if (space == fo->size)