On Wed, Dec 16, 2015 at 1:53 PM, Eric Dumazet <eric.duma...@gmail.com> wrote:
>
> From: Eric Dumazet <eduma...@google.com>
>
> Yuchung tracked a regression caused by commit 57be5bdad759 ("ip: convert
> tcp_sendmsg() to iov_iter primitives") for TCP Fast Open.
>
> Some Fast Open users do not actually add any data in the SYN packet.
>
> Fixes: 57be5bdad759 ("ip: convert tcp_sendmsg() to iov_iter primitives")
> Reported-by: Yuchung Cheng <ych...@google.com>
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Cc: Al Viro <v...@zeniv.linux.org.uk>
> ---
Acked-by: Yuchung Cheng <ych...@google.com>
> net/ipv4/tcp_output.c | 23 ++++++++++++-----------
> 1 file changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index cb7ca569052c..9bfc39ff2285 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -3150,7 +3150,7 @@ static int tcp_send_syn_data(struct sock *sk, struct
> sk_buff *syn)
> {
> struct tcp_sock *tp = tcp_sk(sk);
> struct tcp_fastopen_request *fo = tp->fastopen_req;
> - int syn_loss = 0, space, err = 0, copied;
> + int syn_loss = 0, space, err = 0;
> unsigned long last_syn_loss = 0;
> struct sk_buff *syn_data;
>
> @@ -3188,17 +3188,18 @@ static int tcp_send_syn_data(struct sock *sk, struct
> sk_buff *syn)
> goto fallback;
> syn_data->ip_summed = CHECKSUM_PARTIAL;
> memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
> - copied = copy_from_iter(skb_put(syn_data, space), space,
> - &fo->data->msg_iter);
> - if (unlikely(!copied)) {
> - kfree_skb(syn_data);
> - goto fallback;
> - }
> - if (copied != space) {
> - skb_trim(syn_data, copied);
> - space = copied;
> + if (space) {
> + int copied = copy_from_iter(skb_put(syn_data, space), space,
> + &fo->data->msg_iter);
> + if (unlikely(!copied)) {
> + kfree_skb(syn_data);
> + goto fallback;
> + }
> + if (copied != space) {
> + skb_trim(syn_data, copied);
> + space = copied;
> + }
> }
> -
> /* No more data pending in inet_wait_for_connect() */
> if (space == fo->size)
> fo->data = NULL;
>
>
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