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net/tcp/sendfile: fast retransmit on duplicate acknowledgments (RFC 5681).

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(the same as it was implemented in tcp_send_unbuffered.c)
This commit is contained in:
Alexander Lunev 2022-01-22 01:00:27 +03:00 committed by archer
parent a24ae559c2
commit ad25c43983
2 changed files with 46 additions and 7 deletions
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1
net/tcp/tcp_send_unbuffered.c
View File

@ -293,6 +293,7 @@ static uint16_t tcpsend_eventhandler(FAR struct net_driver_s *dev,
CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK)
{
flags |= TCP_REXMIT;
pstate->snd_dup_acks = 0;
}
}
else

52
net/tcp/tcp_sendfile.c
View File

@ -84,6 +84,15 @@ struct sendfile_s
ssize_t snd_sent; /* The number of bytes sent */
uint32_t snd_isn; /* Initial sequence number */
uint32_t snd_acked; /* The number of bytes acked */
uint32_t snd_prev_ack; /* The previous ACKed seq number */
#ifdef CONFIG_NET_TCP_WINDOW_SCALE
uint32_t snd_prev_wnd; /* The advertised window in the last
* incoming acknowledgment
*/
#else
uint16_t snd_prev_wnd;
#endif
int snd_dup_acks; /* Duplicate ACK counter */
};
/****************************************************************************
@ -218,6 +227,7 @@ static uint16_t sendfile_eventhandler(FAR struct net_driver_s *dev,
if ((flags & TCP_ACKDATA) != 0)
{
uint32_t ackno;
FAR struct tcp_hdr_s *tcp;
/* Get the offset address of the TCP header */
@ -242,14 +252,14 @@ static uint16_t sendfile_eventhandler(FAR struct net_driver_s *dev,
}
#endif /* CONFIG_NET_IPv4 */
/* The current acknowledgement number number is the (relative) offset
/* The current acknowledgement number is the (relative) offset
* of the of the next byte needed by the receiver. The snd_isn is the
* offset of the first byte to send to the receiver. The difference
* is the number of bytes to be acknowledged.
*/
pstate->snd_acked = TCP_SEQ_SUB(tcp_getsequence(tcp->ackno),
pstate->snd_isn);
ackno = tcp_getsequence(tcp->ackno);
pstate->snd_acked = TCP_SEQ_SUB(ackno, pstate->snd_isn);
ninfo("ACK: acked=%" PRId32 " sent=%zd flen=%zu\n",
pstate->snd_acked, pstate->snd_sent, pstate->snd_flen);
@ -264,15 +274,43 @@ static uint16_t sendfile_eventhandler(FAR struct net_driver_s *dev,
goto end_wait;
}
/* No. Fall through to send more data if necessary */
/* Fast Retransmit (RFC 5681): an acknowledgment is considered a
* "duplicate" when (a) the receiver of the ACK has outstanding data,
* (b) the incoming acknowledgment carries no data, (c) the SYN and
* FIN bits are both off, (d) the acknowledgment number is equal to
* the greatest acknowledgment received on the given connection
* and (e) the advertised window in the incoming acknowledgment equals
* the advertised window in the last incoming acknowledgment.
*/
if (pstate->snd_acked < pstate->snd_sent &&
(flags & TCP_NEWDATA) == 0 &&
(tcp->flags & (TCP_SYN | TCP_FIN)) == 0 &&
ackno == pstate->snd_prev_ack &&
conn->snd_wnd == pstate->snd_prev_wnd)
{
if (++pstate->snd_dup_acks >=
CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK)
{
flags |= TCP_REXMIT;
pstate->snd_dup_acks = 0;
}
}
else
{
pstate->snd_dup_acks = 0;
}
pstate->snd_prev_ack = ackno;
pstate->snd_prev_wnd = conn->snd_wnd;
}
/* Check if we are being asked to retransmit data.
* This condition is located here after TCP_ACKDATA for performance reasons
* (TCP_REXMIT is less frequent than TCP_ACKDATA).
* This condition is located here (after TCP_ACKDATA and before
* TCP_DISCONN_EVENTS) for performance reasons.
*/
else if ((flags & TCP_REXMIT) != 0)
if ((flags & TCP_REXMIT) != 0)
{
uint32_t sndlen;