diff options
| -rw-r--r-- | net/ipv4/tcp_output.c | 96 |
1 files changed, 59 insertions, 37 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index a524627923ae..86ef98975e94 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1766,46 +1766,22 @@ u32 __tcp_select_window(struct sock *sk) return window; } -/* Attempt to collapse two adjacent SKB's during retransmission. */ -static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, - int mss_now) +/* Collapses two adjacent SKB's during retransmission. */ +static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); struct sk_buff *next_skb = tcp_write_queue_next(sk, skb); int skb_size, next_skb_size; u16 flags; - /* The first test we must make is that neither of these two - * SKB's are still referenced by someone else. - */ - if (skb_cloned(skb) || skb_cloned(next_skb)) - return; - skb_size = skb->len; next_skb_size = next_skb->len; flags = TCP_SKB_CB(skb)->flags; - /* Also punt if next skb has been SACK'd. */ - if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED) - return; - - /* Next skb is out of window. */ - if (after(TCP_SKB_CB(next_skb)->end_seq, tcp_wnd_end(tp))) - return; - - /* Punt if not enough space exists in the first SKB for - * the data in the second, or the total combined payload - * would exceed the MSS. - */ - if ((next_skb_size > skb_tailroom(skb)) || - ((skb_size + next_skb_size) > mss_now)) - return; - BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1); tcp_highest_sack_combine(sk, next_skb, skb); - /* Ok. We will be able to collapse the packet. */ tcp_unlink_write_queue(next_skb, sk); skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size), @@ -1847,6 +1823,62 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, sk_wmem_free_skb(sk, next_skb); } +static int tcp_can_collapse(struct sock *sk, struct sk_buff *skb) +{ + if (tcp_skb_pcount(skb) > 1) + return 0; + /* TODO: SACK collapsing could be used to remove this condition */ + if (skb_shinfo(skb)->nr_frags != 0) + return 0; + if (skb_cloned(skb)) + return 0; + if (skb == tcp_send_head(sk)) + return 0; + /* Some heurestics for collapsing over SACK'd could be invented */ + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) + return 0; + + return 1; +} + +static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, + int space) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb = to, *tmp; + int first = 1; + + if (!sysctl_tcp_retrans_collapse) + return; + if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) + return; + + tcp_for_write_queue_from_safe(skb, tmp, sk) { + if (!tcp_can_collapse(sk, skb)) + break; + + space -= skb->len; + + if (first) { + first = 0; + continue; + } + + if (space < 0) + break; + /* Punt if not enough space exists in the first SKB for + * the data in the second + */ + if (skb->len > skb_tailroom(to)) + break; + + if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp))) + break; + + tcp_collapse_retrans(sk, to); + } +} + /* Do a simple retransmit without using the backoff mechanisms in * tcp_timer. This is used for path mtu discovery. * The socket is already locked here. @@ -1946,17 +1978,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) return -ENOMEM; /* We'll try again later. */ } - /* Collapse two adjacent packets if worthwhile and we can. */ - if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) && - (skb->len < (cur_mss >> 1)) && - (!tcp_skb_is_last(sk, skb)) && - (tcp_write_queue_next(sk, skb) != tcp_send_head(sk)) && - (skb_shinfo(skb)->nr_frags == 0 && - skb_shinfo(tcp_write_queue_next(sk, skb))->nr_frags == 0) && - (tcp_skb_pcount(skb) == 1 && - tcp_skb_pcount(tcp_write_queue_next(sk, skb)) == 1) && - (sysctl_tcp_retrans_collapse != 0)) - tcp_retrans_try_collapse(sk, skb, cur_mss); + tcp_retrans_try_collapse(sk, skb, cur_mss); /* Some Solaris stacks overoptimize and ignore the FIN on a * retransmit when old data is attached. So strip it off |
