Re: [PATCH net-next] tcp: fix tcp_ofo_queue() to avoid including too much DUP SACK range

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 17 Jun 2025 23:37:06 +0800 xin.guo wrote:
> If the new coming segment covers more than one skbs in the ofo queue,
> and which seq is equal to rcv_nxt , then the sequence range
> that is not duplicated will be sent as DUP SACK,  the detail as below,
> in step6, the {501,2001} range is clearly including too much
> DUP SACK range:
> 1. client.43629 > server.8080: Flags [.], seq 501:1001, ack 1325288529,
> win 20000, length 500: HTTP
> 2. server.8080 > client.43629: Flags [.], ack 1, win 65535, options
> [nop,nop,TS val 269383721 ecr 200,nop,nop,sack 1 {501:1001}], length 0
> 3. Iclient.43629 > server.8080: Flags [.], seq 1501:2001,
> ack 1325288529, win 20000, length 500: HTTP
> 4. server.8080 > client.43629: Flags [.], ack 1, win 65535, options
> [nop,nop,TS val 269383721 ecr 200,nop,nop,sack 2 {1501:2001}
> {501:1001}], length 0
> 5. client.43629 > server.8080: Flags [.], seq 1:2001,
> ack 1325288529, win 20000, length 2000: HTTP
> 6. server.8080 > client.43629: Flags [.], ack 2001, win 65535,
> options [nop,nop,TS val 269383722 ecr 200,nop,nop,sack 1 {501:2001}],
> length 0

Looks reasonable, AFAICT, tho perhaps there's some implicit benefit from
reporting end of the DSACK == rcv_next..

Could you please add the info about how the packet from step 6 looks
"after" this patch? So we have before / after comparison?

With that please resend and make sure you include _all_ maintainers that
the get_maintainer script points out. You missed CCing Eric D.
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