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tcp_input: Accept segments spanning over rcvseq

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This commit is contained in:
YAMAMOTO Takashi 2021-06-18 11:27:09 +09:00 committed by Masayuki Ishikawa
parent eeafe070ec
commit 0886257eb4
1 changed files with 147 additions and 3 deletions
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150
net/tcp/tcp_input.c
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@ -73,6 +73,123 @@
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_trim_head
*
* Description:
* Trim the head of the TCP segment.
*
* Input Parameters:
* dev - The device driver structure containing the received TCP
* packet.
* tcp - The TCP header.
* trimlen - The length to trim in bytes.
*
* Returned Value:
* True if nothing was left.
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
static bool tcp_trim_head(FAR struct net_driver_s *dev,
FAR struct tcp_hdr_s *tcp,
uint32_t trimlen)
{
uint32_t seq = tcp_getsequence(tcp->seqno);
uint16_t urg_ptr = (tcp->urgp[0] << 8) | tcp->urgp[1];
uint32_t urg_trimlen = 0;
uint8_t th_flags = tcp->flags;
DEBUGASSERT(trimlen > 0);
ninfo("Dropping %" PRIu32 " bytes: "
"seq=%" PRIu32 ", "
"tcp flags=%" PRIx8 ", "
"d_len=%" PRIu16 ", "
"urg_ptr=%" PRIu16 "\n",
trimlen,
seq,
th_flags,
dev->d_len,
urg_ptr);
if ((th_flags & TCP_SYN) != 0)
{
ninfo("Dropping SYN\n");
seq = TCP_SEQ_ADD(seq, 1);
urg_trimlen++;
trimlen--;
th_flags &= ~TCP_SYN;
}
if (trimlen > 0)
{
uint32_t len = trimlen;
if (len > dev->d_len)
{
len = dev->d_len;
}
ninfo("Dropping %" PRIu32 " bytes app data\n", len);
seq = TCP_SEQ_ADD(seq, len);
urg_trimlen += len;
dev->d_appdata += len;
dev->d_len -= len;
trimlen -= len;
}
if (trimlen > 0)
{
if ((th_flags & TCP_FIN) != 0)
{
ninfo("Dropping FIN\n");
seq = TCP_SEQ_ADD(seq, 1);
urg_trimlen++;
trimlen--;
th_flags &= ~TCP_FIN;
}
}
/* Update the header */
if ((th_flags & TCP_URG) != 0)
{
/* Adjust URG pointer */
if (urg_trimlen >= urg_ptr)
{
th_flags &= ~TCP_URG;
urg_ptr = 0;
}
else
{
urg_ptr -= urg_trimlen;
}
ninfo("Adjusting URG pointer by %" PRIu32 ", "
"new urg_ptr=%" PRIu16 "\n",
urg_trimlen, urg_ptr);
tcp->urgp[0] = (uint8_t)(urg_ptr >> 8);
tcp->urgp[1] = (uint8_t)urg_ptr;
}
tcp->flags = th_flags;
tcp_setsequence(tcp->seqno, seq);
if ((th_flags & (TCP_SYN | TCP_FIN)) == 0 && dev->d_len == 0)
{
ninfo("Dropped the entire segment\n");
return true;
}
DEBUGASSERT(trimlen == 0);
ninfo("Dropped the segment partially\n");
return false;
}
/****************************************************************************
* Name: tcp_input
*
@ -446,11 +563,38 @@ found:
(((conn->tcpstateflags & TCP_STATE_MASK) == TCP_SYN_RCVD) &&
((tcp->flags & TCP_CTL) == TCP_SYN))))
{
uint32_t seq;
uint32_t rcvseq;
seq = tcp_getsequence(tcp->seqno);
rcvseq = tcp_getsequence(conn->rcvseq);
if ((dev->d_len > 0 || ((tcp->flags & (TCP_SYN | TCP_FIN)) != 0)) &&
memcmp(tcp->seqno, conn->rcvseq, 4) != 0)
seq != rcvseq)
{
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
/* Trim the head of the segment */
if (TCP_SEQ_LT(seq, rcvseq))
{
uint32_t trimlen = TCP_SEQ_SUB(rcvseq, seq);
if (tcp_trim_head(dev, tcp, trimlen))
{
/* The segment was completely out of the window.
* E.g. a retransmit which was not necessary.
*/
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
}
else
{
/* We never queue out-of-order segments. */
tcp_send(dev, conn, TCP_ACK, tcpiplen);
return;
}
}
}