On Fri, Mar 22, 2024 at 10:41 AM Ilya Maximets <i.maxim...@ovn.org> wrote:
>
> Recirculation involves re-parsing the packet from scratch and that
> process is not aware of multiple header levels nor the inner/outer
> offsets. So, it overwrites offsets with new ones from the outermost
> headers and sets offloading flags that change their meaning when
> the packet is marked for tunnel offloading.
>
> For example:
>
> 1. TCP packet enters OVS.
> 2. TCP packet gets encapsulated into UDP tunnel.
> 3. Recirculation happens.
> 4. Packet is re-parsed after recirculation with miniflow_extract()
> or similar function.
> 5. Packet is marked for UDP checksumming because we parse the
> outermost set of headers. But since it is tunneled, it means
> inner UDP checksumming. And that makes no sense, because the
> inner packet is TCP.
>
> This is causing packet drops due to malformed packets or even
> assertions and crashes in the code that is trying to fixup checksums
> for packets using incorrect metadata:
>
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
>
> lib/packets.c:2061:15: runtime error:
> member access within null pointer of type 'struct udp_header'
>
> 0 0xbe5221 in packet_udp_complete_csum lib/packets.c:2061:15
> 1 0x7e5662 in dp_packet_ol_send_prepare lib/dp-packet.c:638:9
> 2 0x96ef89 in netdev_send lib/netdev.c:940:9
> 3 0x818e94 in dp_netdev_pmd_flush_output_on_port lib/dpif-netdev.c:5577:9
> 4 0x817606 in dp_netdev_pmd_flush_output_packets lib/dpif-netdev.c:5618:27
> 5 0x81cfa5 in dp_netdev_process_rxq_port lib/dpif-netdev.c:5677:9
> 6 0x7eefe4 in dpif_netdev_run lib/dpif-netdev.c:7001:25
> 7 0x610e87 in type_run ofproto/ofproto-dpif.c:367:9
> 8 0x5b9e80 in ofproto_type_run ofproto/ofproto.c:1879:31
> 9 0x55bbb4 in bridge_run__ vswitchd/bridge.c:3281:9
> 10 0x558b6b in bridge_run vswitchd/bridge.c:3346:5
> 11 0x591dc5 in main vswitchd/ovs-vswitchd.c:130:9
> 12 0x172b89 in __libc_start_call_main (/lib64/libc.so.6+0x27b89)
> 13 0x172c4a in __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x27c4a)
> 14 0x47eff4 in _start (vswitchd/ovs-vswitchd+0x47eff4)
>
> Tests added for both IPv4 and IPv6 cases. Though IPv6 test doesn't
> trigger the issue it's better to have a symmetric test.
>
> Fixes: 084c8087292c ("userspace: Support VXLAN and GENEVE TSO.")
> Reported-at:
> https://mail.openvswitch.org/pipermail/ovs-discuss/2024-March/053014.html
> Signed-off-by: Ilya Maximets <i.maxim...@ovn.org>
> ---
I have tested this, and it does fix the segfault here.
Acked-by: Mike Pattrick <m...@redhat.com>
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