On Sun, Apr 22, 2018 at 04:47:48PM -0600, David Ahern wrote: > This commit breaks my FIB forwarding program: > > commit 6870de435b90c083ae0f3f7f341287976ef56f03 > Author: Nikita V. Shirokov <tehn...@tehnerd.com> > Date: Tue Apr 17 21:42:20 2018 -0700 > > bpf: make virtio compatible w/ bpf_xdp_adjust_tail > > w/ bpf_xdp_adjust_tail helper xdp's data_end pointer could be changed as > well (only "decrease" of pointer's location is going to be supported). > changing of this pointer will change packet's size. > for virtio driver we need to adjust XDP_PASS handling by recalculating > length of the packet if it was passed to the TCP/IP stack > > Reviewed-by: Jason Wang <jasow...@redhat.com> > Signed-off-by: Nikita V. Shirokov <tehn...@tehnerd.com> > Signed-off-by: Daniel Borkmann <dan...@iogearbox.net> > > ### > > Some of the packets (e.g., ARP or those without a resolved neighbor) are > passed to the networking stack. What shows up are clearly broken packets: > > # tcpdump -n -i eth1 > tcpdump: verbose output suppressed, use -v or -vv for full protocol decode > listening on eth1, link-type EN10MB (Ethernet), capture size 262144 bytes > 15:45:29.693238 [|ARP] > 0x0000: 0001 0800 0604 0001 42c0 ce2f 3fa9 0a64 ........B../?..d > 15:45:30.710327 [|ARP] > 0x0000: 0001 0800 0604 0001 42c0 ce2f 3fa9 0a64 ........B../?..d > 15:45:31.734296 [|ARP] > 0x0000: 0001 0800 0604 0001 42c0 ce2f 3fa9 0a64 ........B../?..d > 15:45:32.908720 IP6 truncated-ip6 - 12 bytes > missing!fe80::40c0:ceff:fe2f:3fa9 > ff02::1:ff00:2: ICMP6, neighbor > solicitation[|icmp6] > 15:45:33.910530 IP6 truncated-ip6 - 12 bytes missing!2001:db8:1::64 > > ff02::1:ff00:2: ICMP6, neighbor solicitation[|icmp6] > 15:45:34.934437 IP6 truncated-ip6 - 12 bytes missing!2001:db8:1::64 > > ff02::1:ff00:2: ICMP6, neighbor solicitation[|icmp6] > 15:45:35.958394 IP6 truncated-ip6 - 12 bytes missing!2001:db8:1::64 > > ff02::1:ff00:2: ICMP6, neighbor solicitation[|icmp6] > > Reverting the mentioned patch fixes the problem. Hi, David. thanks for reporting this. looks like in my calculation i've missed vi->hdr_len during new lengths calculation (it was len = xdp->data_end - xdp->data; but also shouldbe +vi->hdr_len). will run few more tests before sending a fix.
-- Nikita
