The tftp server in FreeBSD fails to send any packets -- when a write request comes in (in this example, from a Cisco IOS router), tcpdump shows that FreeBSD receives the write reqeust but then its tftp server never sends a single packet out in response, and the transfer never starts: Dec 5 14:22:29 <ftp.info> bat tftpd[453]: Filename: 'moat-confg' Dec 5 14:22:29 <ftp.info> bat tftpd[453]: Mode: 'octet' Dec 5 14:22:29 <ftp.info> bat tftpd[453]: 172.27.0.1: write request for //moat-confg: success Dec 5 14:22:34 <ftp.warn> bat tftpd[453]: Timeout #0 on DATA block 1 Dec 5 14:22:39 <ftp.warn> bat tftpd[453]: Timeout #1 on DATA block 1 Dec 5 14:22:44 <ftp.warn> bat tftpd[453]: Timeout #2 on DATA block 1 Dec 5 14:22:49 <ftp.warn> bat tftpd[453]: Timeout #3 on DATA block 1 Dec 5 14:22:54 <ftp.warn> bat tftpd[453]: Timeout #4 on DATA block 1 Dec 5 14:22:59 <ftp.err> bat tftpd[453]: Timeout #5 on DATA block 1, giving up On a complete whim, I tried disabling TSO4, TXCSUM, and RXCSUM on the NIC, and to my surprise I found that disabling the latter two made the problem disappear. TSO had no effect -- as you'd expect since tftp is UDP based :) I have not checked to see if this is em(4) specific or what other UDP based services it might affect. It appears that DNS on the same system works fine... Fix: ifconfig em0 -rxcsum -txcsum (It doesn't appear you can turn just one or the other off.) How-To-Repeat: On a system with an Intel gigabit NIC, start a tftp server (via inetd) and try to write a file to it.
Responsible Changed From-To: freebsd-bugs->freebsd-net Over to maintainer(s).
Some folowup for kern/152853 with a patch. It seems that the current version of if_em.c (both CURRENT and STABLE8) with txcsum/rxcsum cannot send any UDP packet shorter then TCP header size. The reason is suspicious m_pullup(m_head, poff + sizeof(struct tcphdr)) in common packet em_xmit handling. I've moved this m_pullupi() call to required branches further down and this fixed the issue (UDP ack from tftpd daemon now ok). The code however needs some audit, repeated m_pullups are strange. Sincerely, Petr Lampa *** if_em.c.old 2011-01-18 15:52:21.000000000 +0100 --- if_em.c 2011-01-18 15:58:11.000000000 +0100 *************** *** 1820,1831 **** } ip = (struct ip *)(mtod(m_head, char *) + ip_off); poff = ip_off + (ip->ip_hl << 2); - m_head = m_pullup(m_head, poff + sizeof(struct tcphdr)); - if (m_head == NULL) { - *m_headp = NULL; - return (ENOBUFS); - } if (do_tso) { tp = (struct tcphdr *)(mtod(m_head, char *) + poff); /* * TSO workaround: --- 1820,1831 ---- } ip = (struct ip *)(mtod(m_head, char *) + ip_off); poff = ip_off + (ip->ip_hl << 2); if (do_tso) { + m_head = m_pullup(m_head, poff + sizeof(struct tcphdr)); + if (m_head == NULL) { + *m_headp = NULL; + return (ENOBUFS); + } tp = (struct tcphdr *)(mtod(m_head, char *) + poff); /* * TSO workaround: *************** *** 1849,1854 **** --- 1849,1859 ---- tp->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, htons(IPPROTO_TCP)); } else if (m_head->m_pkthdr.csum_flags & CSUM_TCP) { + m_head = m_pullup(m_head, poff + sizeof(struct tcphdr)); + if (m_head == NULL) { + *m_headp = NULL; + return (ENOBUFS); + } tp = (struct tcphdr *)(mtod(m_head, char *) + poff); m_head = m_pullup(m_head, poff + (tp->th_off << 2)); if (m_head == NULL) { -- Computer Centre E-mail: lampa@fit.vutbr.cz Faculty of Information Technology Web: http://www.fit.vutbr.cz/ Brno University of Technology Fax: +420 54114-1270 Bozetechova 2, 612 66 Brno, Czech Republic Phone: +420 54114-1225
Hi! 7.4-PRERELEASE is affected too. In short, tftp is broken in recent em(4) driver in all branches due to this bug. 8.1-RELEASE is not affected, 7.3 is fine too. Eugene Grosbein
This appears to be applied to if_em.c ... if this is not the case, please correctly reopen this ticket.