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Remove if #if 0 logic. Update some comments.

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This commit is contained in:
Gregory Nutt 2018-06-24 15:50:45 -06:00
parent 715d561c41
commit 25686a9dac
1 changed files with 11 additions and 23 deletions
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34
net/tcp/tcp_send.c
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@ -315,7 +315,6 @@ static void tcp_sendcommon(FAR struct net_driver_s *dev,
FAR struct tcp_hdr_s *tcp)
{
#ifdef CONFIG_NET_TCP_RWND_CONTROL
uint32_t rwnd;
uint16_t iplen;
uint16_t overhead;
int navail;
@ -371,11 +370,17 @@ static void tcp_sendcommon(FAR struct net_driver_s *dev,
navail = iob_navail();
if (navail > 0)
{
uint32_t rwnd;
/* The optimal TCP window size is the amount of TCP data that we can
* currently buffer via TCP read-ahead buffering minus overhead for the
* link-layer, IP, and TCP headers. This logic here assumes that
* all IOBs are available for TCP buffering.
*
* Assume that all of the available IOBs are can be used for buffering
* on this connection. Also assume that at least one chain is available
* concatenate the IOBs.
*
* REVISIT: In an environment with multiple, active read-ahead TCP
* sockets (and perhaps multiple network devices) or if there are
* other consumers of IOBs (such as for TCP write buffering) then the
@ -383,41 +388,24 @@ static void tcp_sendcommon(FAR struct net_driver_s *dev,
* buffering for this connection.
*/
#if 0
/* REVISIT: (1)CONFIG_NET_ETH_TCP_RECVWNDO will typically be larger
* than the IOB payload size. (2) Why divide by CONFIG_IOB_NCHAINS?
* (3) CONFIG_NET_ETH_TCP_RECVWNDO includes the header overhead
* penalty. But we only have to pay the header overhead penalty
* once. (4) This logic needs to work even if Ethernet is not
* enabled (and hence CONFIG_NET_ETH_TCP_RECVWNDO is not defined).
*/
rwnd = (navail * CONFIG_NET_ETH_TCP_RECVWNDO) / CONFIG_IOB_NCHAINS;
#else
/* Assume that all of the available IOBs are can be used for buffering
* on this connection.
*/
rwnd = (navail * CONFIG_IOB_BUFSIZE) - overhead;
#endif
/* Save the new receive window size */
if (rwnd > UINT16_MAX)
{
rwnd = UINT16_MAX;
}
/* Save the new receive window size */
NET_DEV_RCVWNDO(dev) = (uint16_t)rwnd;
}
else /* (navail == 0) */
else /* if (navail == 0) */
{
/* No IOBs are available... fall back to the configured default
* which assumes no write buffering. The only buffering available
* is the packet itself.
* is within the packet buffer itself.
*
* NOTE: If no IOBs are available, then the next packet will be
* lost will be be lost if there is no listener on the connection.
* lost if there is no listener on the connection.
*/
NET_DEV_RCVWNDO(dev) = dev->d_mtu - overhead;