lwIP - A Lightweight TCP/IP stack - Bugs: bug #63092, When the length of unack data is...
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bug #63092: When the length of unack data is less than pcb->cwnd, LWIP cannot send packets.
Submitter: | jiangheng <jinag12345> | ||
Submitted: | Fri 23 Sep 2022 10:14:28 AM UTC | ||
Category: | TCP | Severity: | 3 - Normal |
Item Group: | None | Status: | None |
Privacy: | Public | Assigned to: | None |
Open/Closed: | Open | Planned Release: | None |
lwIP version: | 2.1.3 |
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Items that depend on this one: None found
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In tcp_output function:
if (lwip_ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > wnd) {
....
goto output_done;
}
In tcp_slowmgr function:
if (pcb->rtime >= pcb->rto) {
pcb->cwnd = pcb->mss;
tcp_rexmit_rto_commit(pcb);
}
tcp_rexmit_rto_commit ≈ tcp_output;
in tcp_output, The printf command output is as follows:
lwip_ntohl(seg->tcphdr->seqno) = 405161
pcb->lastack = 403701
seg->len = 1460
pcb->snd_wnd 65535
pcb->cwnd = 1460
so tcp_output will not send this tcp segment, It enters the slow start phase of congestion control and cannot exit.
Although unack data exists, the value of snd_wnd is 65535. lwip cant send data is correct this moment?