Re: [PATCH v2] tcp: probe for SO_PEEK_OFF both in tcpv4 and tcp6

On Wed, 24 Jul 2024 13:31:49 +1000
David Gibson <david(a)gibson.dropbear.id.au> wrote:

...
  On Wed, Jul 24, 2024 at 10:40:15AM +1000, David Gibson
wrote:
  On Tue, Jul 23, 2024 at 10:29:36PM +0200, Stefano
Brivio wrote:  
  On Tue, 23 Jul 2024 00:09:37 +0200
 Stefano Brivio <sbrivio(a)redhat.com> wrote:
   
  From: Jon Maloy <jmaloy(a)redhat.com>
 
 Based on an original patch by Jon Maloy:
    
 
 ...so, with this, the probing issue is solved: on a 6.10 kernel,
 SO_PEEK_OFF is not used, unless I disable IPv6 (with --ipv4-only / -4).
 
 However, if I disable it, for some reason, resorting to IPv4, at least
 together with the flow table (applying just this patch to HEAD), I get
 something that looks like one of the "old" TCP stalls. On the host:
 
   $ ./passt -f -t 10000 -4
 
 and in the guest:
 
   # ip link set dev eth0 up
   # dhclient eth0
   # iperf3 -s -p 10000
 
 back to the host:
 
   $ iperf3 -c 127.0.0.1 -p 10000
   Connecting to host 127.0.0.1, port 10000
   [  5] local 127.0.0.1 port 39046 connected to 127.0.0.1 port 10000
   [ ID] Interval           Transfer     Bitrate         Retr  Cwnd
   [  5]   0.00-1.00   sec  11.2 MBytes  94.3 Mbits/sec    0   5.50 MBytes       
   [  5]   1.00-2.00   sec  0.00 Bytes  0.00 bits/sec    0   5.50 MBytes       
   [  5]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec    0   5.50 MBytes       
 
 ...the transfer never recovers.   
 
 Bother.  I've reproduced and am debugging now.   
 
 Found it.  Looks like one of the cases where we need to set
 SO_PEEK_OFF was lost somewhere in the refactorings :(. 
Hah, great, thanks, it fixes the issue on my setup as well. Re-running
all tests now...

-- 
Stefano