95% of the time my ftp/telnet apps work fine. However, once in awhile I get into a cycle where the tcp connections totally hose up. The cause appears to be related to the fact that in sys_mbox_fetch(), the again:/goto again loop is spinning with wild abandon. I put a counter inside sys_mbox_fetch, which easily upticks into the several hundreds within seconds of stack startup. I've verified that the sys_arch_mbox_fetch is returning sane values. The odd thing is that this only crops up once in awhile, and will stay around. Last time I thought I had a bad ethernet card, and switched test targets, and everything started working. However, now that I'm seeing it again on different hardware/ethernet card combo, I'm concerned that I've got a critical bug floating around somewhere.
I've attached a wireshark capture of the link output. It's a portion of the ftp session. You'll see that it basically works, but will spew out loads of TCP Dup ACK, TCP Retransmits, and finally drops the connection at the end with a series of 7 RSTs in a row. Presumably I'm seeing these cause the timers are firing way to fast.
Note: This is a custom port of lwIP to an OS I'm working on.
Any ideas on how to debug this, or what the issue is? When this occurs, I do have an inetd server start listening on several tcp ports at system startup.
Thanks
-- Thomas Taranowski Expert embedded software design/contracting address@hidden (remove the n0sp4m)
crazed_ftp.pcap