Roger, > Adding the persons that contributed that code in case they can shed some > light. > > El 03/11/15 a les 21.12, Larry Baird ha escrit: > > Has anybody made any progress on "Bug 188261 - [xen] FreeBSD DomU PVHVM > > guests cannot 'route' traffic for other Xen PV guests on same Dom0 Host." > > (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=188261)? > > > > The code for checksum calculation in the function xnb_add_mbuf_cksum() looks > > suspect. > > > > switch (iph->ip_p) { > > case IPPROTO_TCP: > > if (mbufc->m_pkthdr.csum_flags & CSUM_IP_VALID) { > > size_t tcplen = ntohs(iph->ip_len) - sizeof(struct > > ip); > > struct tcphdr *th = (struct tcphdr*)(iph + 1); > > th->th_sum = in_pseudo(iph->ip_src.s_addr, > > iph->ip_dst.s_addr, htons(IPPROTO_TCP + > > tcplen)); > > th->th_sum = in_cksum_skip(mbufc, > > sizeof(struct ether_header) + > > ntohs(iph->ip_len), > > sizeof(struct ether_header) + (iph->ip_hl << > > 2)); > > } > > break; > > case IPPROTO_UDP: > > if (mbufc->m_pkthdr.csum_flags & CSUM_IP_VALID) { > > size_t udplen = ntohs(iph->ip_len) - sizeof(struct > > ip); > > struct udphdr *uh = (struct udphdr*)(iph + 1); > > uh->uh_sum = in_pseudo(iph->ip_src.s_addr, > > iph->ip_dst.s_addr, htons(IPPROTO_UDP + > > udplen)); > > uh->uh_sum = in_cksum_skip(mbufc, > > sizeof(struct ether_header) + > > ntohs(iph->ip_len), > > sizeof(struct ether_header) + (iph->ip_hl << > > 2)); > > } > > break; > > default: > > break; > > } > > > > > > Both in_pseudo() and in_cksum_skip() set the same checksum. Does this > > make since to anybody? > > The bug you are referring to affects FreeBSD when running as a guest > using xen-netfront, but the code snipped above and the function > referenced (xnb_add_mbuf_cksum) is only used on FreeBSD when running as > a host (AKA Dom0) by xen-netback. > > TBH, I don't know that much about FreeBSD network subsystem to have an > opinion, but it certainly looks weird. Patches are welcome :).
Xyper-V has a similar forward issue. I found they were misusing csum_flags and were always attempting to do checksum offloading if CSUM_IP_VALID was set. I have given them a patch that fixes the issue. I was hoping that Xen's issue was similar. I found the issue above by looking at all uses of csum_flags in sys/dev/xen. It is hard to tell what the correct fix is, without fulling understand the protocal used when communicating between backend and frontend of Xen. I am sure issue with XEN guest forwarding has to with checksum offloading. If I am not misinterpreting your comments, I can ignore code in netback and concentrate on code in netfront when trying to understand what is going wrong. Thank you for some insite, Larry -- ------------------------------------------------------------------------ Larry Baird Global Technology Associates, Inc. 1992-2012 | http://www.gta.com Celebrating Twenty Years of Software Innovation | Orlando, FL Email: l...@gta.com | TEL 407-380-0220 _______________________________________________ freebsd-xen@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-xen To unsubscribe, send any mail to "freebsd-xen-unsubscr...@freebsd.org"