On Fri, Feb 17, 2023 at 06:22:57PM -0500, Xin Long wrote: > For IPv6 Jumbo packets, the ipv6_hdr(skb)->payload_len is always 0, > and its real payload_len ( > 65535) is saved in hbh exthdr. With 0 > length for the jumbo packets, it may mismatch. > > To fix this, we can just use skb->len instead of parsing exthdrs, as > the hbh exthdr parsing has been done before coming to length_mt6 in > ip6_rcv_core() and br_validate_ipv6() and also the packet has been > trimmed according to the correct IPv6 (ext)hdr length there, and skb > len is trustable in length_mt6(). > > Note that this patch is especially needed after the IPv6 BIG TCP was > supported in kernel, which is using IPv6 Jumbo packets. Besides, to > match the packets greater than 65535 more properly, a v1 revision of > xt_length may be needed to extend "min, max" to u32 in the future, > and for now the IPv6 Jumbo packets can be matched by: > > # ip6tables -m length ! --length 0:65535 Applied, thanks
