• David Howells's avatar
    rxrpc: Add a timeout for detecting lost ACKs/lost DATA · bd1fdf8c
    David Howells authored
    Add an extra timeout that is set/updated when we send a DATA packet that
    has the request-ack flag set.  This allows us to detect if we don't get an
    ACK in response to the latest flagged packet.
    
    The ACK packet is adjudged to have been lost if it doesn't turn up within
    2*RTT of the transmission.
    
    If the timeout occurs, we schedule the sending of a PING ACK to find out
    the state of the other side.  If a new DATA packet is ready to go sooner,
    we cancel the sending of the ping and set the request-ack flag on that
    instead.
    
    If we get back a PING-RESPONSE ACK that indicates a lower tx_top than what
    we had at the time of the ping transmission, we adjudge all the DATA
    packets sent between the response tx_top and the ping-time tx_top to have
    been lost and retransmit immediately.
    
    Rather than sending a PING ACK, we could just pick a DATA packet and
    speculatively retransmit that with request-ack set.  It should result in
    either a REQUESTED ACK or a DUPLICATE ACK which we can then use in lieu the
    a PING-RESPONSE ACK mentioned above.
    Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
    bd1fdf8c
rxrpc.h 33.4 KB