diff options
| author | Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> | 2010-09-15 10:27:52 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-09-26 17:21:20 -0700 |
| commit | 36f2140e8f572790a71899e9db7ff6f2986987cd (patch) | |
| tree | 0e7d612cecf9b2a01a9966f708742e66e3c5845f /include/net | |
| parent | f99150007ae1ff46aefbd5c96cf22af0cdc34563 (diff) | |
tcp: Prevent overzealous packetization by SWS logic.
[ Upstream commit 01f83d69844d307be2aa6fea88b0e8fe5cbdb2f4 ]
If peer uses tiny MSS (say, 75 bytes) and similarly tiny advertised
window, the SWS logic will packetize to half the MSS unnecessarily.
This causes problems with some embedded devices.
However for large MSS devices we do want to half-MSS packetize
otherwise we never get enough packets into the pipe for things
like fast retransmit and recovery to work.
Be careful also to handle the case where MSS > window, otherwise
we'll never send until the probe timer.
Reported-by: ツ Leandro Melo de Sales <leandroal@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'include/net')
| -rw-r--r-- | include/net/tcp.h | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 6bc4ac02de0..6cfe18bc2c0 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -511,8 +511,22 @@ extern unsigned int tcp_current_mss(struct sock *sk); /* Bound MSS / TSO packet size with the half of the window */ static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize) { - if (tp->max_window && pktsize > (tp->max_window >> 1)) - return max(tp->max_window >> 1, 68U - tp->tcp_header_len); + int cutoff; + + /* When peer uses tiny windows, there is no use in packetizing + * to sub-MSS pieces for the sake of SWS or making sure there + * are enough packets in the pipe for fast recovery. + * + * On the other hand, for extremely large MSS devices, handling + * smaller than MSS windows in this way does make sense. + */ + if (tp->max_window >= 512) + cutoff = (tp->max_window >> 1); + else + cutoff = tp->max_window; + + if (cutoff && pktsize > cutoff) + return max_t(int, cutoff, 68U - tp->tcp_header_len); else return pktsize; } |