diff options
Diffstat (limited to 'net/ipv4/tcp_ipv4.c')
| -rw-r--r-- | net/ipv4/tcp_ipv4.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 4a8ec457310..8cdee120a50 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1950,6 +1950,50 @@ void tcp_v4_early_demux(struct sk_buff *skb) } } +/* Packet is added to VJ-style prequeue for processing in process + * context, if a reader task is waiting. Apparently, this exciting + * idea (VJ's mail "Re: query about TCP header on tcp-ip" of 07 Sep 93) + * failed somewhere. Latency? Burstiness? Well, at least now we will + * see, why it failed. 8)8) --ANK + * + */ +bool tcp_prequeue(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (sysctl_tcp_low_latency || !tp->ucopy.task) + return false; + + if (skb->len <= tcp_hdrlen(skb) && + skb_queue_len(&tp->ucopy.prequeue) == 0) + return false; + + __skb_queue_tail(&tp->ucopy.prequeue, skb); + tp->ucopy.memory += skb->truesize; + if (tp->ucopy.memory > sk->sk_rcvbuf) { + struct sk_buff *skb1; + + BUG_ON(sock_owned_by_user(sk)); + + while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) { + sk_backlog_rcv(sk, skb1); + NET_INC_STATS_BH(sock_net(sk), + LINUX_MIB_TCPPREQUEUEDROPPED); + } + + tp->ucopy.memory = 0; + } else if (skb_queue_len(&tp->ucopy.prequeue) == 1) { + wake_up_interruptible_sync_poll(sk_sleep(sk), + POLLIN | POLLRDNORM | POLLRDBAND); + if (!inet_csk_ack_scheduled(sk)) + inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, + (3 * tcp_rto_min(sk)) / 4, + TCP_RTO_MAX); + } + return true; +} +EXPORT_SYMBOL(tcp_prequeue); + /* * From tcp_input.c */ |