On 8/15/24 22:03, Mike Pattrick wrote:
> During the transition towards checksum offloading, the function to
> handle software fallback of IPv4 checksums didn't account for the
> options field.
>
> Fixes: 5d11c47d3ebe ("userspace: Enable IP checksum offloading by default.")
> Reported-by: Jun Wang <[email protected]>
> Signed-off-by: Mike Pattrick <[email protected]>
> ---
> NB: In 3.2 the early checksum offloading patches caused packets from
> the netdev-dummy/receive appctl command to resolve checksums prior to
> odp-execute. This fixed in 3.3, but that can't easily be backported
> without also backporting unrelated code.
>
> To enable this patch to be backported, I gave one of the packets a
> correct checksum and changed the comment so it was correct but also the
> same number of lines as in the previous patch.
>
Hi, Mike. Thanks for looking into this, but I'm still a bit confused
about what is going on. The packets in the test do not trigger the
dp_packet_ip_set_header_csum() call, i.e. these tests do not actually
test the code change in this patch. However, the previous ${bad_frame}
does trigger the function and the checksum is re-calculated for it.
What's the difference between these two? Are IP options affecting the
logic somehow?
Best regards, Ilya Maximets.
> ---
> lib/dp-packet.h | 11 +++++++++--
> tests/dpif-netdev.at | 35 +++++++++++++++++++++++++++++++++++
> 2 files changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/lib/dp-packet.h b/lib/dp-packet.h
> index 70ddf8aa4..25a0d31a1 100644
> --- a/lib/dp-packet.h
> +++ b/lib/dp-packet.h
> @@ -1142,10 +1142,17 @@ static inline void
> dp_packet_ip_set_header_csum(struct dp_packet *p)
> {
> struct ip_header *ip = dp_packet_l3(p);
> + size_t l3_size = dp_packet_l3_size(p);
> + size_t ip_len;
>
> ovs_assert(ip);
> - ip->ip_csum = 0;
> - ip->ip_csum = csum(ip, sizeof *ip);
> +
> + ip_len = IP_IHL(ip->ip_ihl_ver) * 4;
> +
> + if (OVS_LIKELY(ip_len >= IP_HEADER_LEN && ip_len < l3_size)) {
> + ip->ip_csum = 0;
> + ip->ip_csum = csum(ip, ip_len);
> + }
> }
>
> /* Returns 'true' if the packet 'p' has good integrity and the
> diff --git a/tests/dpif-netdev.at b/tests/dpif-netdev.at
> index 061e13af8..93226521a 100644
> --- a/tests/dpif-netdev.at
> +++ b/tests/dpif-netdev.at
> @@ -807,6 +807,41 @@ AT_CHECK([ovs-appctl netdev-dummy/receive p1
> ${bad_frame}])
> AT_CHECK([ovs-pcap p2.pcap > p2.pcap.txt 2>&1])
> AT_CHECK_UNQUOTED([tail -n 1 p2.pcap.txt], [0], [${good_expected}
> ])
> +
> +dnl Test with IP optional fields in a valid packet. Note that this packet
> +dnl contains a correct checksum, but the following packet doesn't. This is
> +dnl because the dummy interface resets checksum offload on packet recipt.
> +m4_define([OPT_PKT], m4_join([],
> +dnl eth(dst=aa:aa:aa:aa:aa:aa,src=bb:bb:bb:bb:bb:bb,type=0x0800)
> +[aaaaaaaaaaaabbbbbbbbbbbb0800],
> +dnl ipv4(dst=10.0.0.2,src=10.0.0.1,proto=1,len=60,tot_len=68,csum=0x94d6)
> +[4f000044abab0000400194d60a0000010a000002],
> +dnl IPv4 Opt: type 7 (Record Route) len 39 + type 0 (EOL).
> +[07270c010203040a000003000000000000000000],
> +[0000000000000000000000000000000000000000],
> +dnl icmp(type=8,code=0), csum 0x3e2f incorrect, should be 0x412f.
> +[08003e2fb6d00000]))
> +
> +dnl IP header indicates optional fields but doesn't contain any.
> +m4_define([MICROGRAM], m4_join([],
> +dnl eth(dst=aa:aa:aa:aa:aa:aa,src=bb:bb:bb:bb:bb:bb,type=0x0800)
> +[aaaaaaaaaaaabbbbbbbbbbbb0800],
> +dnl ipv4(dst=10.0.0.2,src=10.0.0.1,proto=1,len=60,tot_len=68,csum=0xeeee)
> +[4f000044abab00004001eeee0a0000010a000002]))
> +
> +AT_CHECK([ovs-vsctl set Interface p1 options:ol_ip_csum=true])
> +AT_CHECK([ovs-vsctl set Interface p1 options:ol_ip_csum_set_good=true])
> +AT_CHECK([ovs-appctl netdev-dummy/receive p1 OPT_PKT])
> +AT_CHECK([ovs-appctl netdev-dummy/receive p1 MICROGRAM])
> +AT_CHECK([ovs-pcap p2.pcap > p2.pcap.txt 2>&1])
> +
> +dnl Build the expected modified packets. The first packet has a valid IPv4
> +dnl checksum and modified destination IP address. The second packet isn't
> +dnl expected to change.
> +AT_CHECK([echo "OPT_PKT" | sed -e "s/0a000002/c0a80101/" -e "s/94d6/dd2e/" >
> expout])
> +AT_CHECK([echo "MICROGRAM" >> expout])
> +AT_CHECK([tail -n 2 p2.pcap.txt], [0], [expout])
> +
> OVS_VSWITCHD_STOP
> AT_CLEANUP
>
> --
> 2.43.5
>
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