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SubjectRe: Honoring SO_RCVLOWAT in proto_ops.poll methods
On Sun, Oct 05, 2008 at 01:27:22PM -0700, David Miller wrote:
>
> Give this patch a try:
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 1ab341e..0e43875 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -384,13 +384,17 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
>
> /* Connected? */
> if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV)) {
> + int target = sock_rcvlowat(sk, 0, INT_MAX);
> +
> + if (tp->urg_seq == tp->copied_seq &&
> + !sock_flag(sk, SOCK_URGINLINE) &&
> + tp->urg_data)
> + target--;
> +
> /* Potential race condition. If read of tp below will
> * escape above sk->sk_state, we can be illegally awaken
> * in SYN_* states. */
> - if ((tp->rcv_nxt != tp->copied_seq) &&
> - (tp->urg_seq != tp->copied_seq ||
> - tp->rcv_nxt != tp->copied_seq + 1 ||
> - sock_flag(sk, SOCK_URGINLINE) || !tp->urg_data))
> + if (target >= tp->rcv_nxt - tp->copied_seq)
> mask |= POLLIN | POLLRDNORM;
>
> if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {


I will be testing this patch today. At a glance it appears with this
patch we're still not taking rcvlowat into consideration in recv()
with MSG_PEEK flag set. This should probably also be corrected, as
mentioned in the thread previously.

Regards,
Vito Caputo


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