| Message ID | 148968163004.20909.2389917167977671935.stgit@warthog.procyon.org.uk |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: David Howells <dhowells@redhat.com> Date: Thu, 16 Mar 2017 16:27:10 +0000 > If we receive a BUSY packet for a call we think we've just completed, the > packet is handed off to the connection processor to deal with - but the > connection processor doesn't expect a BUSY packet and so flags a protocol > error. > > Fix this by simply ignoring the BUSY packet for the moment. > > The symptom of this may appear as a system call failing with EPROTO. This > may be triggered by pressing ctrl-C under some circumstances. > > This comes about we abort calls due to interruption by a signal (which we > shouldn't do, but that's going to be a large fix and mostly in fs/afs/). > What happens is that we abort the call and may also abort follow up calls > too (this needs offloading somehoe). So we see a transmission of something > like the following sequence of packets: > > DATA for call N > ABORT call N > DATA for call N+1 > ABORT call N+1 > > in very quick succession on the same channel. However, the peer may have > deferred the processing of the ABORT from the call N to a background thread > and thus sees the DATA message from the call N+1 coming in before it has > cleared the channel. Thus it sends a BUSY packet[*]. > > [*] Note that some implementations (OpenAFS, for example) mark the BUSY > packet with one plus the callNumber of the call prior to call N. > Ordinarily, this would be call N, but there's no requirement for the > calls on a channel to be numbered strictly sequentially (the number is > required to increase). > > This is wrong and means that the callNumber in the BUSY packet should > be ignored (it really ought to be N+1 since that's what it's in > response to). > > Signed-off-by: David Howells <dhowells@redhat.com> Applied, thanks David.
diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c index 3f9d8d7ec632..b099b64366f3 100644 --- a/net/rxrpc/conn_event.c +++ b/net/rxrpc/conn_event.c @@ -275,6 +275,10 @@ static int rxrpc_process_event(struct rxrpc_connection *conn, rxrpc_conn_retransmit_call(conn, skb); return 0; + case RXRPC_PACKET_TYPE_BUSY: + /* Just ignore BUSY packets for now. */ + return 0; + case RXRPC_PACKET_TYPE_ABORT: if (skb_copy_bits(skb, sizeof(struct rxrpc_wire_header), &wtmp, sizeof(wtmp)) < 0)
If we receive a BUSY packet for a call we think we've just completed, the packet is handed off to the connection processor to deal with - but the connection processor doesn't expect a BUSY packet and so flags a protocol error. Fix this by simply ignoring the BUSY packet for the moment. The symptom of this may appear as a system call failing with EPROTO. This may be triggered by pressing ctrl-C under some circumstances. This comes about we abort calls due to interruption by a signal (which we shouldn't do, but that's going to be a large fix and mostly in fs/afs/). What happens is that we abort the call and may also abort follow up calls too (this needs offloading somehoe). So we see a transmission of something like the following sequence of packets: DATA for call N ABORT call N DATA for call N+1 ABORT call N+1 in very quick succession on the same channel. However, the peer may have deferred the processing of the ABORT from the call N to a background thread and thus sees the DATA message from the call N+1 coming in before it has cleared the channel. Thus it sends a BUSY packet[*]. [*] Note that some implementations (OpenAFS, for example) mark the BUSY packet with one plus the callNumber of the call prior to call N. Ordinarily, this would be call N, but there's no requirement for the calls on a channel to be numbered strictly sequentially (the number is required to increase). This is wrong and means that the callNumber in the BUSY packet should be ignored (it really ought to be N+1 since that's what it's in response to). Signed-off-by: David Howells <dhowells@redhat.com> --- net/rxrpc/conn_event.c | 4 ++++ 1 file changed, 4 insertions(+)