linux-kernel - Re: [PATCH net-next v2 2/3] net: gro: parse ipv6 ext headers without frag0 invalidation

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Date: Wed, 3 Jan 2024 15:01:15 +0100
From: Richard Gobert <richardbgobert@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, dsahern@...nel.org, kuba@...nel.org,
 pabeni@...hat.com, shuah@...nel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/3] net: gro: parse ipv6 ext headers without
 frag0 invalidation

Eric Dumazet wrote:

> 
> 
> Hmm... I was looking at
> 
> skb_checksum_setup_ipv6() , it uses skb_maybe_pull_tail( ...
> sizeof(struct ipv6_opt_hdr))
> ipv6_skip_exthdr()  also uses sizeof(struct ipv6_opt_hdr)
> ip6_tnl_parse_tlv_enc_lim also uses the same.
> hbh_mt6(), ipv6header_mt6(),  .. same...
> ip6_find_1stfragopt(), get_ipv6_ext_hdrs(), tcf_csum_ipv6(),
> mip6_rthdr_offset() same
> 
> So it seems you found two helpers that went the other way.
> 
> If you think pulling 8 bytes first is a win, I would suggest a stand
> alone patch, adding the magic constant
> using it in all places, so that a casual reader can make sense of the
> magical 8 value.

I guess pulling 8 bytes first is not such a big advantage.
I will submit a v3 with sizeof(*opth) as you suggested.