Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
[TCP]: DSACK signals data receival, be conservative
In case a DSACK is received, it's better to lower cwnd as it's
a sign of data receival.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
authored by Ilpo Järvinen and committed by David S. Miller 49ff4bb4 2e605294
+4
-1
net/ipv4/tcp_input.c
+4
-1
net/ipv4/tcp_input.c
···
103
#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104
#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
105
#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
106
107
#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
108
#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
···
967
968
/* Check for D-SACK. */
969
if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) {
970
found_dup_sack = 1;
971
tp->rx_opt.sack_ok |= 4;
972
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
973
} else if (num_sacks > 1 &&
974
!after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) &&
975
!before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) {
976
found_dup_sack = 1;
977
tp->rx_opt.sack_ok |= 4;
978
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
···
1861
struct tcp_sock *tp = tcp_sk(sk);
1862
int decr = tp->snd_cwnd_cnt + 1;
1863
1864
-
if ((flag&FLAG_ANY_PROGRESS) ||
1865
(IsReno(tp) && !(flag&FLAG_NOT_DUP))) {
1866
tp->snd_cwnd_cnt = decr&1;
1867
decr >>= 1;
···
103
#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104
#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
105
#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
106
+
#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained DSACK info */
107
108
#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
109
#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
···
966
967
/* Check for D-SACK. */
968
if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) {
969
+
flag |= FLAG_DSACKING_ACK;
970
found_dup_sack = 1;
971
tp->rx_opt.sack_ok |= 4;
972
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
973
} else if (num_sacks > 1 &&
974
!after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) &&
975
!before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) {
976
+
flag |= FLAG_DSACKING_ACK;
977
found_dup_sack = 1;
978
tp->rx_opt.sack_ok |= 4;
979
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
···
1858
struct tcp_sock *tp = tcp_sk(sk);
1859
int decr = tp->snd_cwnd_cnt + 1;
1860
1861
+
if ((flag&(FLAG_ANY_PROGRESS|FLAG_DSACKING_ACK)) ||
1862
(IsReno(tp) && !(flag&FLAG_NOT_DUP))) {
1863
tp->snd_cwnd_cnt = decr&1;
1864
decr >>= 1;