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tcp: Avoid unnecessary ACK

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E.g. Avoid Dup ACK in packet #981

979 4.115432000 192.168.66.123 -> 192.168.66.100 TCP 20406
    [TCP Window Full] 10000 > 50112 [ACK] Seq=10675905 Ack=801512443 Win=3737600 Len=20352

980 4.119002000 192.168.66.100 -> 192.168.66.123 TCP 54
    [TCP ZeroWindow] 50112 > 10000 [ACK] Seq=801512443 Ack=10696257 Win=0 Len=0

981 4.119063000 192.168.66.123 -> 192.168.66.100 TCP 54
    [TCP Dup ACK 979#1] 10000 > 50112 [ACK] Seq=10696257 Ack=801512443 Win=3737600 Len=0

982 4.137244000 192.168.66.100 -> 192.168.66.123 TCP 54
    [TCP Window Update] 50112 > 10000 [ACK] Seq=801512443 Ack=10696257 Win=40704 Len=0
This commit is contained in:
Asias He
2014-11-07 16:25:27 +08:00
committed by Avi Kivity
parent 5b994fb4f0
commit ff674d3e0e
1 changed files with 5 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
net/tcp.hh
View File

@@ -470,6 +470,7 @@ void tcp<InetTraits>::tcb::input(tcp_hdr* th, packet p) {
p.trim_front(th->data_offset * 4);
bool do_output = false;
bool do_output_data = false;
tcp_seq seg_seq = th->seq;
auto seg_len = p.len();
@@ -554,6 +555,7 @@ void tcp<InetTraits>::tcb::input(tcp_hdr* th, packet p) {
// If this <FIN> packet contains data as well, we can ACK both data
// and <FIN> in a single packet, so canncel the previous ACK.
clear_delayed_ack();
do_output = false;
output();
// FIXME: Implement TIME-WAIT state
@@ -602,9 +604,7 @@ void tcp<InetTraits>::tcb::input(tcp_hdr* th, packet p) {
}
// some data is acked, try send more data
if (can_send() > 0) {
do_output = true;
}
do_output_data = true;
if (_snd.data.empty()) {
// All outstanding segments are acked, turn off the timer.
@@ -632,14 +632,14 @@ void tcp<InetTraits>::tcb::input(tcp_hdr* th, packet p) {
if (th->seq >= _snd.wl1 && th->ack >= _snd.wl2) {
if (!_snd.window && th->window && _snd.unsent_len) {
do_output = true;
do_output_data = true;
}
_snd.window = th->window << _snd.window_scale;
_snd.wl1 = th->seq;
_snd.wl2 = th->ack;
}
// send some stuff
if (do_output) {
if (do_output || (do_output_data && can_send())) {
output();
}
}