Pankaj,
> In file vnet/ip/ip6_forward.c(VPP 21.01), function ip6_local_inline(),
> the node's packet processing has the following check:
>
> if (PREDICT_FALSE (need_csum))
> {
> flags = ip6_tcp_udp_icmp_validate_checksum (vm, b[0]);
> good_l4_csum = flags & VNET_BUFFER_F_L4_CHECKSUM_CORRECT;
> error = IP6_ERROR_UNKNOWN_PROTOCOL;
> }
> else
> {
> if (ip6_tcp_udp_icmp_bad_length (vm, b[0]))
> error = IP6_ERROR_BAD_LENGTH;
> }
>
> Kindly explain the reason behind the checksum and the length validation being
> under the if-else check, making the length validation not applicable for the
> case when checksum validation is applicable.
>
> Also, in the function ip6_tcp_udp_icmp_bad_length (refer the below snippet),
> the function seems to assume that the hop-by-hop extension header shall
> always be present. Is it that, IPv6 hop-by-hop extension header has to be
> mandatorily present?
Indeed. That code looks quite questionable.
A good start would perhaps be to write tests showing where it fails? Then that
will make refactoring and fixing afterwards.
Best regards,
Ole
>
> static_always_inline u8
> ip6_tcp_udp_icmp_bad_length (vlib_main_t * vm, vlib_buffer_t * p0)
> {
>
> u16 payload_length_host_byte_order;
> u32 n_this_buffer, n_bytes_left;
> ip6_header_t *ip0 = vlib_buffer_get_current (p0);
> u32 headers_size = sizeof (ip0[0]);
> u8 *data_this_buffer;
>
> data_this_buffer = (u8 *) (ip0 + 1);
>
> ip6_hop_by_hop_ext_t *ext_hdr = (ip6_hop_by_hop_ext_t *) data_this_buffer;
>
> /* validate really icmp6 next */
>
> if (!(ext_hdr->next_hdr == IP_PROTOCOL_ICMP6)
> || (ext_hdr->next_hdr == IP_PROTOCOL_UDP))
> return 0;
> ::
> ::
>
>
> Thanks,
> Pankaj Malhotra
>
>
>
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