OpenAFS doesn't always correctly terminate client calls that it makes -
this includes calls the OpenAFS servers make to the cache manager service.
It should end the client call with either:
(1) An ACK that has firstPacket set to one greater than the seq number of
the reply DATA packet with the LAST_PACKET flag set (thereby
hard-ACK'ing all packets). nAcks should be 0 and acks[] should be
empty (ie. no soft-ACKs).
(2) An ACKALL packet.
OpenAFS, though, may send an ACK packet with firstPacket set to the last
seq number or less and soft-ACKs listed for all packets up to and including
the last DATA packet.
The transmitter, however, is obliged to keep the call live and the
soft-ACK'd DATA packets around until they're hard-ACK'd as the receiver is
permitted to drop any merely soft-ACK'd packet and request retransmission
by sending an ACK packet with a NACK in it.
Further, OpenAFS will also terminate a client call by beginning the next
client call on the same connection channel. This implicitly completes the
previous call.
This patch handles implicit ACK of a call on a channel by the reception of
the first packet of the next call on that channel.
If another call doesn't come along to implicitly ACK a call, then we have
to time the call out. There are some bugs there that will be addressed in
subsequent patches.
Signed-off-by: David Howells <dhowells@redhat.com>
b3156274ca