* [PATCH v2] tcp: make retransmitted SKB fit into the send window
@ 2022-07-08 8:59 Yonglong Li
2022-07-08 11:45 ` Eric Dumazet
0 siblings, 1 reply; 4+ messages in thread
From: Yonglong Li @ 2022-07-08 8:59 UTC (permalink / raw)
To: netdev; +Cc: davem, dsahern, edumazet, kuba, pabeni, liyonglong
From: lyl <liyonglong@chinatelecom.cn>
current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq
in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window.
If receiver has shrunk his window, and skb is out of new window, it
should not retransmit it.
test packetdrill script:
0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
+0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
+0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
+0 > S 0:0(0) win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
+.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK>
+0 > . 1:1(0) ack 1
+0 write(3, ..., 10000) = 10000
+0 > . 1:2001(2000) ack 1 win 65535
+0 > . 2001:4001(2000) ack 1 win 65535
+0 > . 4001:6001(2000) ack 1 win 65535
+.05 < . 1:1(0) ack 4001 win 1001
and tcpdump show:
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000
192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
when cient retract window to 1001, send window is [4001,5002],
but TLP send 5001-6001 packet which is out of send window.
Signed-off-by: liyonglong <liyonglong@chinatelecom.cn>
---
net/ipv4/tcp_output.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 1c05443..7e1569e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3176,7 +3176,12 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
TCP_SKB_CB(skb)->seq != tp->snd_una)
return -EAGAIN;
- len = cur_mss * segs;
+ len = min_t(int, tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq, cur_mss * segs);
+
+ /* retransmit serves as a zero window probe. */
+ if (len == 0 && TCP_SKB_CB(skb)->seq == tp->snd_una)
+ len = cur_mss;
+
if (skb->len > len) {
if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
cur_mss, GFP_ATOMIC))
--
1.8.3.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] tcp: make retransmitted SKB fit into the send window
2022-07-08 8:59 [PATCH v2] tcp: make retransmitted SKB fit into the send window Yonglong Li
@ 2022-07-08 11:45 ` Eric Dumazet
2022-07-11 1:53 ` Yonglong Li
0 siblings, 1 reply; 4+ messages in thread
From: Eric Dumazet @ 2022-07-08 11:45 UTC (permalink / raw)
To: Yonglong Li
Cc: netdev, David Miller, David Ahern, Jakub Kicinski, Paolo Abeni
On Fri, Jul 8, 2022 at 10:59 AM Yonglong Li <liyonglong@chinatelecom.cn> wrote:
>
> From: lyl <liyonglong@chinatelecom.cn>
>
> current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq
> in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window.
> If receiver has shrunk his window, and skb is out of new window, it
> should not retransmit it.
More exactly, it should retransmit a smaller portion of the payload.
>
> test packetdrill script:
> 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
> +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
> +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
>
> +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
> +0 > S 0:0(0) win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
> +.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK>
> +0 > . 1:1(0) ack 1
>
> +0 write(3, ..., 10000) = 10000
>
> +0 > . 1:2001(2000) ack 1 win 65535
> +0 > . 2001:4001(2000) ack 1 win 65535
> +0 > . 4001:6001(2000) ack 1 win 65535
>
> +.05 < . 1:1(0) ack 4001 win 1001
>
> and tcpdump show:
> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000
> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000
> 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
> 192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0
> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
> 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
>
> when cient retract window to 1001, send window is [4001,5002],
> but TLP send 5001-6001 packet which is out of send window.
>
> Signed-off-by: liyonglong <liyonglong@chinatelecom.cn>
> ---
> net/ipv4/tcp_output.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 1c05443..7e1569e 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -3176,7 +3176,12 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
> TCP_SKB_CB(skb)->seq != tp->snd_una)
> return -EAGAIN;
>
> - len = cur_mss * segs;
> + len = min_t(int, tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq, cur_mss * segs);
> +
> + /* retransmit serves as a zero window probe. */
> + if (len == 0 && TCP_SKB_CB(skb)->seq == tp->snd_una)
> + len = cur_mss;
> +
I asked in my prior feeback to align len to a multiple of cur_mss.
Trying to send full MSS is likely helping receivers to not waste
memory and thus send us bigger RWIN.
Also I think the logic about zero window probe could be consolidated
in one place.
Also you forgot to change the part about tcp_retrans_try_collapse()
which I also mentioned in my feedback.
If we want to fix this problem for good, we need to take care of all cases...
Something like this:
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 18c913a2347a984ae8cf2793bb8991e59e5e94ab..2aa67cbfa1428a11b723263083ce48284762e306
100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3144,7 +3144,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct
sk_buff *skb, int segs)
struct tcp_sock *tp = tcp_sk(sk);
unsigned int cur_mss;
int diff, len, err;
-
+ int avail_wnd;
/* Inconclusive MTU probe */
if (icsk->icsk_mtup.probe_size)
@@ -3167,16 +3167,24 @@ int __tcp_retransmit_skb(struct sock *sk,
struct sk_buff *skb, int segs)
cur_mss = tcp_current_mss(sk);
+ avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
/* If receiver has shrunk his window, and skb is out of
* new window, do not retransmit it. The exception is the
* case, when window is shrunk to zero. In this case
- * our retransmit serves as a zero window probe.
+ * our retransmit of one segment serves as a zero window probe.
*/
- if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
- TCP_SKB_CB(skb)->seq != tp->snd_una)
- return -EAGAIN;
+ if (avail_wnd <= 0) {
+ if (TCP_SKB_CB(skb)->seq != tp->snd_una)
+ return -EAGAIN;
+ avail_wnd = cur_mss;
+ }
len = cur_mss * segs;
+ if (len > avail_wnd) {
+ len = rounddown(avail_wnd, cur_mss);
+ if (!len)
+ len = avail_wnd;
+ }
if (skb->len > len) {
if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
cur_mss, GFP_ATOMIC))
@@ -3190,8 +3198,9 @@ int __tcp_retransmit_skb(struct sock *sk, struct
sk_buff *skb, int segs)
diff -= tcp_skb_pcount(skb);
if (diff)
tcp_adjust_pcount(sk, skb, diff);
- if (skb->len < cur_mss)
- tcp_retrans_try_collapse(sk, skb, cur_mss);
+ avail_wnd = min_t(int, avail_wnd, cur_mss);
+ if (skb->len < avail_wnd)
+ tcp_retrans_try_collapse(sk, skb, avail_wnd);
}
/* RFC3168, section 6.1.1.1. ECN fallback */
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] tcp: make retransmitted SKB fit into the send window
2022-07-08 11:45 ` Eric Dumazet
@ 2022-07-11 1:53 ` Yonglong Li
2022-07-11 6:39 ` Eric Dumazet
0 siblings, 1 reply; 4+ messages in thread
From: Yonglong Li @ 2022-07-11 1:53 UTC (permalink / raw)
To: Eric Dumazet
Cc: netdev, David Miller, David Ahern, Jakub Kicinski, Paolo Abeni
Hi Eric,
thank you for your feedback and suggestions. Sorry for miss part of your
prior feedback. I will prepare a v3 patch as your suggestion.
And anther your feedback about "need a Fixes: tag", I can not find any commit
which is related to this patch. Do you have any suggestion about Fixes:tag?
On 7/8/2022 7:45 PM, Eric Dumazet wrote:
> On Fri, Jul 8, 2022 at 10:59 AM Yonglong Li <liyonglong@chinatelecom.cn> wrote:
>>
>> From: lyl <liyonglong@chinatelecom.cn>
>>
>> current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq
>> in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window.
>> If receiver has shrunk his window, and skb is out of new window, it
>> should not retransmit it.
>
> More exactly, it should retransmit a smaller portion of the payload.
>
>>
>> test packetdrill script:
>> 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
>> +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
>> +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
>>
>> +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
>> +0 > S 0:0(0) win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
>> +.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK>
>> +0 > . 1:1(0) ack 1
>>
>> +0 write(3, ..., 10000) = 10000
>>
>> +0 > . 1:2001(2000) ack 1 win 65535
>> +0 > . 2001:4001(2000) ack 1 win 65535
>> +0 > . 4001:6001(2000) ack 1 win 65535
>>
>> +.05 < . 1:1(0) ack 4001 win 1001
>>
>> and tcpdump show:
>> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000
>> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000
>> 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
>> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
>> 192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0
>> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
>> 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
>>
>> when cient retract window to 1001, send window is [4001,5002],
>> but TLP send 5001-6001 packet which is out of send window.
>>
>> Signed-off-by: liyonglong <liyonglong@chinatelecom.cn>
>> ---
>> net/ipv4/tcp_output.c | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
>> index 1c05443..7e1569e 100644
>> --- a/net/ipv4/tcp_output.c
>> +++ b/net/ipv4/tcp_output.c
>> @@ -3176,7 +3176,12 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
>> TCP_SKB_CB(skb)->seq != tp->snd_una)
>> return -EAGAIN;
>>
>> - len = cur_mss * segs;
>> + len = min_t(int, tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq, cur_mss * segs);
>> +
>> + /* retransmit serves as a zero window probe. */
>> + if (len == 0 && TCP_SKB_CB(skb)->seq == tp->snd_una)
>> + len = cur_mss;
>> +
>
> I asked in my prior feeback to align len to a multiple of cur_mss.
> Trying to send full MSS is likely helping receivers to not waste
> memory and thus send us bigger RWIN.
>
> Also I think the logic about zero window probe could be consolidated
> in one place.
>
> Also you forgot to change the part about tcp_retrans_try_collapse()
> which I also mentioned in my feedback.
>
> If we want to fix this problem for good, we need to take care of all cases...
>
> Something like this:
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 18c913a2347a984ae8cf2793bb8991e59e5e94ab..2aa67cbfa1428a11b723263083ce48284762e306
> 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -3144,7 +3144,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct
> sk_buff *skb, int segs)
> struct tcp_sock *tp = tcp_sk(sk);
> unsigned int cur_mss;
> int diff, len, err;
> -
> + int avail_wnd;
>
> /* Inconclusive MTU probe */
> if (icsk->icsk_mtup.probe_size)
> @@ -3167,16 +3167,24 @@ int __tcp_retransmit_skb(struct sock *sk,
> struct sk_buff *skb, int segs)
>
> cur_mss = tcp_current_mss(sk);
>
> + avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
> /* If receiver has shrunk his window, and skb is out of
> * new window, do not retransmit it. The exception is the
> * case, when window is shrunk to zero. In this case
> - * our retransmit serves as a zero window probe.
> + * our retransmit of one segment serves as a zero window probe.
> */
> - if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
> - TCP_SKB_CB(skb)->seq != tp->snd_una)
> - return -EAGAIN;
> + if (avail_wnd <= 0) {
> + if (TCP_SKB_CB(skb)->seq != tp->snd_una)
> + return -EAGAIN;
> + avail_wnd = cur_mss;
> + }
>
> len = cur_mss * segs;
> + if (len > avail_wnd) {
> + len = rounddown(avail_wnd, cur_mss);
> + if (!len)
> + len = avail_wnd;
> + }
> if (skb->len > len) {
> if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
> cur_mss, GFP_ATOMIC))
> @@ -3190,8 +3198,9 @@ int __tcp_retransmit_skb(struct sock *sk, struct
> sk_buff *skb, int segs)
> diff -= tcp_skb_pcount(skb);
> if (diff)
> tcp_adjust_pcount(sk, skb, diff);
> - if (skb->len < cur_mss)
> - tcp_retrans_try_collapse(sk, skb, cur_mss);
> + avail_wnd = min_t(int, avail_wnd, cur_mss);
> + if (skb->len < avail_wnd)
> + tcp_retrans_try_collapse(sk, skb, avail_wnd);
> }
>
> /* RFC3168, section 6.1.1.1. ECN fallback */
>
--
Li YongLong
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] tcp: make retransmitted SKB fit into the send window
2022-07-11 1:53 ` Yonglong Li
@ 2022-07-11 6:39 ` Eric Dumazet
0 siblings, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2022-07-11 6:39 UTC (permalink / raw)
To: Yonglong Li
Cc: netdev, David Miller, David Ahern, Jakub Kicinski, Paolo Abeni
On Mon, Jul 11, 2022 at 3:54 AM Yonglong Li <liyonglong@chinatelecom.cn> wrote:
>
> Hi Eric,
> thank you for your feedback and suggestions. Sorry for miss part of your
> prior feedback. I will prepare a v3 patch as your suggestion.
>
> And anther your feedback about "need a Fixes: tag", I can not find any commit
> which is related to this patch. Do you have any suggestion about Fixes:tag?
This could be the following, because I do not think linux ever got this right.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>
> On 7/8/2022 7:45 PM, Eric Dumazet wrote:
> > On Fri, Jul 8, 2022 at 10:59 AM Yonglong Li <liyonglong@chinatelecom.cn> wrote:
> >>
> >> From: lyl <liyonglong@chinatelecom.cn>
> >>
> >> current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq
> >> in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window.
> >> If receiver has shrunk his window, and skb is out of new window, it
> >> should not retransmit it.
> >
> > More exactly, it should retransmit a smaller portion of the payload.
> >
> >>
> >> test packetdrill script:
> >> 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
> >> +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
> >> +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
> >>
> >> +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
> >> +0 > S 0:0(0) win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
> >> +.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK>
> >> +0 > . 1:1(0) ack 1
> >>
> >> +0 write(3, ..., 10000) = 10000
> >>
> >> +0 > . 1:2001(2000) ack 1 win 65535
> >> +0 > . 2001:4001(2000) ack 1 win 65535
> >> +0 > . 4001:6001(2000) ack 1 win 65535
> >>
> >> +.05 < . 1:1(0) ack 4001 win 1001
> >>
> >> and tcpdump show:
> >> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000
> >> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000
> >> 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
> >> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
> >> 192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0
> >> 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
> >> 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
> >>
> >> when cient retract window to 1001, send window is [4001,5002],
> >> but TLP send 5001-6001 packet which is out of send window.
> >>
> >> Signed-off-by: liyonglong <liyonglong@chinatelecom.cn>
> >> ---
> >> net/ipv4/tcp_output.c | 7 ++++++-
> >> 1 file changed, 6 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> >> index 1c05443..7e1569e 100644
> >> --- a/net/ipv4/tcp_output.c
> >> +++ b/net/ipv4/tcp_output.c
> >> @@ -3176,7 +3176,12 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
> >> TCP_SKB_CB(skb)->seq != tp->snd_una)
> >> return -EAGAIN;
> >>
> >> - len = cur_mss * segs;
> >> + len = min_t(int, tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq, cur_mss * segs);
> >> +
> >> + /* retransmit serves as a zero window probe. */
> >> + if (len == 0 && TCP_SKB_CB(skb)->seq == tp->snd_una)
> >> + len = cur_mss;
> >> +
> >
> > I asked in my prior feeback to align len to a multiple of cur_mss.
> > Trying to send full MSS is likely helping receivers to not waste
> > memory and thus send us bigger RWIN.
> >
> > Also I think the logic about zero window probe could be consolidated
> > in one place.
> >
> > Also you forgot to change the part about tcp_retrans_try_collapse()
> > which I also mentioned in my feedback.
> >
> > If we want to fix this problem for good, we need to take care of all cases...
> >
> > Something like this:
> >
> > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> > index 18c913a2347a984ae8cf2793bb8991e59e5e94ab..2aa67cbfa1428a11b723263083ce48284762e306
> > 100644
> > --- a/net/ipv4/tcp_output.c
> > +++ b/net/ipv4/tcp_output.c
> > @@ -3144,7 +3144,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct
> > sk_buff *skb, int segs)
> > struct tcp_sock *tp = tcp_sk(sk);
> > unsigned int cur_mss;
> > int diff, len, err;
> > -
> > + int avail_wnd;
> >
> > /* Inconclusive MTU probe */
> > if (icsk->icsk_mtup.probe_size)
> > @@ -3167,16 +3167,24 @@ int __tcp_retransmit_skb(struct sock *sk,
> > struct sk_buff *skb, int segs)
> >
> > cur_mss = tcp_current_mss(sk);
> >
> > + avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
> > /* If receiver has shrunk his window, and skb is out of
> > * new window, do not retransmit it. The exception is the
> > * case, when window is shrunk to zero. In this case
> > - * our retransmit serves as a zero window probe.
> > + * our retransmit of one segment serves as a zero window probe.
> > */
> > - if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
> > - TCP_SKB_CB(skb)->seq != tp->snd_una)
> > - return -EAGAIN;
> > + if (avail_wnd <= 0) {
> > + if (TCP_SKB_CB(skb)->seq != tp->snd_una)
> > + return -EAGAIN;
> > + avail_wnd = cur_mss;
> > + }
> >
> > len = cur_mss * segs;
> > + if (len > avail_wnd) {
> > + len = rounddown(avail_wnd, cur_mss);
> > + if (!len)
> > + len = avail_wnd;
> > + }
> > if (skb->len > len) {
> > if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
> > cur_mss, GFP_ATOMIC))
> > @@ -3190,8 +3198,9 @@ int __tcp_retransmit_skb(struct sock *sk, struct
> > sk_buff *skb, int segs)
> > diff -= tcp_skb_pcount(skb);
> > if (diff)
> > tcp_adjust_pcount(sk, skb, diff);
> > - if (skb->len < cur_mss)
> > - tcp_retrans_try_collapse(sk, skb, cur_mss);
> > + avail_wnd = min_t(int, avail_wnd, cur_mss);
> > + if (skb->len < avail_wnd)
> > + tcp_retrans_try_collapse(sk, skb, avail_wnd);
> > }
> >
> > /* RFC3168, section 6.1.1.1. ECN fallback */
> >
>
> --
> Li YongLong
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-07-11 6:40 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-07-08 8:59 [PATCH v2] tcp: make retransmitted SKB fit into the send window Yonglong Li
2022-07-08 11:45 ` Eric Dumazet
2022-07-11 1:53 ` Yonglong Li
2022-07-11 6:39 ` Eric Dumazet
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