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net/tcp: transformed NET_TCP_FAST_RETRANSMIT_WATERMARK option to boolean.

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According to RFC 5681 (3.2) the TCP Fast Retransmit algorithm should start
if the threshold of 3 duplicate ACKs is reached.
Thus the threshold should be a constant, not an integer option.
This commit is contained in:
Alexander Lunev 2022-01-25 20:49:04 +03:00 committed by archer
parent ecccc614bd
commit 2a6de301ee
6 changed files with 29 additions and 11 deletions
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6
net/tcp/Kconfig
View File

@ -79,9 +79,9 @@ config NET_MAX_LISTENPORTS
---help---
Maximum number of listening TCP/IP ports (all tasks). Default: 20
config NET_TCP_FAST_RETRANSMIT_WATERMARK
int "WaterMark to trigger Fast Retransmission"
default 3
config NET_TCP_FAST_RETRANSMIT
bool "Enable the Fast Retransmit algorithm"
default y
---help---
RFC2001:
3. Fast Retransmit

10
net/tcp/tcp.h
View File

@ -65,7 +65,9 @@
# define TCP_WBPKTLEN(wrb) ((wrb)->wb_iob->io_pktlen)
# define TCP_WBSENT(wrb) ((wrb)->wb_sent)
# define TCP_WBNRTX(wrb) ((wrb)->wb_nrtx)
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
# define TCP_WBNACK(wrb) ((wrb)->wb_nack)
#endif
# define TCP_WBIOB(wrb) ((wrb)->wb_iob)
# define TCP_WBCOPYOUT(wrb,dest,n) (iob_copyout(dest,(wrb)->wb_iob,(n),0))
# define TCP_WBCOPYIN(wrb,src,n,off) \
@ -101,6 +103,12 @@
#define TCP_WSCALE 0x01U /* Window Scale option enabled */
/* After receiving 3 duplicate ACKs, TCP performs a retransmission
* (RFC 5681 (3.2))
*/
#define TCP_FAST_RETRANSMISSION_THRESH 3
/****************************************************************************
* Public Type Definitions
****************************************************************************/
@ -330,7 +338,9 @@ struct tcp_wrbuffer_s
uint16_t wb_sent; /* Number of bytes sent from the I/O buffer chain */
uint8_t wb_nrtx; /* The number of retransmissions for the last
* segment sent */
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
uint8_t wb_nack; /* The number of ack count */
#endif
struct iob_s *wb_iob; /* Head of the I/O buffer chain */
};
#endif

8
net/tcp/tcp_send_buffered.c
View File

@ -543,6 +543,7 @@ static uint16_t psock_send_eventhandler(FAR struct net_driver_s *dev,
wrb, TCP_WBSEQNO(wrb), TCP_WBPKTLEN(wrb));
}
}
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
else if (ackno == TCP_WBSEQNO(wrb))
{
/* Reset the duplicate ack counter */
@ -554,15 +555,13 @@ static uint16_t psock_send_eventhandler(FAR struct net_driver_s *dev,
/* Duplicate ACK? Retransmit data if need */
if (++TCP_WBNACK(wrb) ==
CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK)
if (++TCP_WBNACK(wrb) == TCP_FAST_RETRANSMISSION_THRESH)
{
/* Do fast retransmit */
rexmit = true;
}
else if ((TCP_WBNACK(wrb) >
CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK) &&
else if ((TCP_WBNACK(wrb) > TCP_FAST_RETRANSMISSION_THRESH) &&
TCP_WBNACK(wrb) == sq_count(&conn->unacked_q) - 1)
{
/* Reset the duplicate ack counter */
@ -570,6 +569,7 @@ static uint16_t psock_send_eventhandler(FAR struct net_driver_s *dev,
TCP_WBNACK(wrb) = 0;
}
}
#endif
}
/* A special case is the head of the write_q which may be partially

7
net/tcp/tcp_send_unbuffered.c
View File

@ -88,6 +88,7 @@ struct send_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 */
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
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
@ -97,6 +98,7 @@ struct send_s
uint16_t snd_prev_wnd;
#endif
int snd_dup_acks; /* Duplicate ACK counter */
#endif
};
/****************************************************************************
@ -274,6 +276,7 @@ static uint16_t tcpsend_eventhandler(FAR struct net_driver_s *dev,
goto end_wait;
}
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
/* 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
@ -289,8 +292,7 @@ static uint16_t tcpsend_eventhandler(FAR struct net_driver_s *dev,
ackno == pstate->snd_prev_ack &&
conn->snd_wnd == pstate->snd_prev_wnd)
{
if (++pstate->snd_dup_acks >=
CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK)
if (++pstate->snd_dup_acks >= TCP_FAST_RETRANSMISSION_THRESH)
{
flags |= TCP_REXMIT;
pstate->snd_dup_acks = 0;
@ -303,6 +305,7 @@ static uint16_t tcpsend_eventhandler(FAR struct net_driver_s *dev,
pstate->snd_prev_ack = ackno;
pstate->snd_prev_wnd = conn->snd_wnd;
#endif
}
/* Check if we are being asked to retransmit data.

7
net/tcp/tcp_sendfile.c
View File

@ -84,6 +84,7 @@ 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 */
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
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
@ -93,6 +94,7 @@ struct sendfile_s
uint16_t snd_prev_wnd;
#endif
int snd_dup_acks; /* Duplicate ACK counter */
#endif
};
/****************************************************************************
@ -227,6 +229,7 @@ static uint16_t sendfile_eventhandler(FAR struct net_driver_s *dev,
goto end_wait;
}
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
/* 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
@ -242,8 +245,7 @@ static uint16_t sendfile_eventhandler(FAR struct net_driver_s *dev,
ackno == pstate->snd_prev_ack &&
conn->snd_wnd == pstate->snd_prev_wnd)
{
if (++pstate->snd_dup_acks >=
CONFIG_NET_TCP_FAST_RETRANSMIT_WATERMARK)
if (++pstate->snd_dup_acks >= TCP_FAST_RETRANSMISSION_THRESH)
{
flags |= TCP_REXMIT;
pstate->snd_dup_acks = 0;
@ -256,6 +258,7 @@ static uint16_t sendfile_eventhandler(FAR struct net_driver_s *dev,
pstate->snd_prev_ack = ackno;
pstate->snd_prev_wnd = conn->snd_wnd;
#endif
}
/* Check if we are being asked to retransmit data.

2
net/tcp/tcp_wrbuffer.c
View File

@ -243,9 +243,11 @@ void tcp_wrbuffer_release(FAR struct tcp_wrbuffer_s *wrb)
iob_free_chain(wrb->wb_iob, IOBUSER_NET_TCP_WRITEBUFFER);
}
#ifdef CONFIG_NET_TCP_FAST_RETRANSMIT
/* Reset the ack counter */
TCP_WBNACK(wrb) = 0;
#endif
/* Then free the write buffer structure */