Can you see this issue with the 5.4 kernel too? I did yesterday some testing by upgrading kernel from 5.4 to 5.7 and I run into all sorts of links going off after a while so I had to revert back. 5.4 is stable for me. 5.7 is not. And I have lots of M2PA and M3UA connections like you > On 8 Oct 2020, at 23:46, David Laight <David.Laight@xxxxxxxxxx> wrote: > > One of my local tests (that I run quite often) failed in a 'new and exciting way'. > I sent 510 messages through an M3UA-MTP2-M3UA link and only got ~350 at the far end. > (This is part of my SS7+TCAP regression test - gets run a lot.) > Usually I can find 'lost' messages logged as discarded due to my own flow control. > In this case there is no sign of any error traces. > I expect to have each message traced 6 times (on each send and receive) > but the missing messages are only traced 5 times. > > Now /proc/net/sctp/snmp has SctpInDataChunksDiscards set to 163, > this matches the number of messages I'm missing. > Any idea how I can find out why one (or more) the SCTP connections (which are still > connected - unless there is a power cut) has discarded a lot of receive packets? > > Each M3UA link is actually 4 SCTP connections (TCP style 1-1). > All are loopback connected to 127.0.0.1 or ::1 (the assocs print is 'interesting'). > The local port is 'random' the listening port 2905 or 2906. > I'd expect the data to loadshare evenly between them but I've not checked the actual > distribution. > The packet data contains a sequence number, I'm missing all the x1, x2, x9, xa > and half the x6 and xe packets - so I think at least one of the sctp connections > is just discarding the receive chunks. > (I'll sort out which one tomorrow.) > > This is a 5.6.0-rc7 kernel. > I've not seen anything like this before - I've run this same test for > over 10 years, probably going back to at least 2.6.28. > > Data chunks will have gone though all the connections when they were > initialised. > > Is there anything anywhere that indicates why a data chunk was dropped? > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >
