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Message-ID: <9480856d183c88a205fd79d9dbc156a7fd3ea0d3.camel@redhat.com>
Date: Tue, 29 Nov 2022 10:33:59 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Coco Li <lixiaoyan@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
David Ahern <dsahern@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Michael Chan <michael.chan@...adcom.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/2] IPv6/GRO: generic helper to remove
temporary HBH/jumbo header in driver
Hello,
Only a couple of minor things below, reporting them as this is still a
RFC, right ? ;)
On Wed, 2022-11-23 at 11:16 -0800, Coco Li wrote:
> IPv6/TCP and GRO stacks can build big TCP packets with an added
> temporary Hop By Hop header.
>
> Is GSO is not involved, then the temporary header needs to be removed in
> the driver. This patch provides a generic helper for drivers that need
> to modify their headers in place.
>
> Signed-off-by: Coco Li <lixiaoyan@...gle.com>
> ---
> include/net/ipv6.h | 36 ++++++++++++++++++++++++++++++++++++
> net/ipv6/ip6_offload.c | 26 ++++----------------------
> 2 files changed, 40 insertions(+), 22 deletions(-)
>
> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> index d383c895592a..c5a1daaf5056 100644
> --- a/include/net/ipv6.h
> +++ b/include/net/ipv6.h
> @@ -500,6 +500,42 @@ static inline int ipv6_has_hopopt_jumbo(const struct sk_buff *skb)
> return jhdr->nexthdr;
> }
>
> +/* Return 0 if HBH header is successfully removed
> + * Or if HBH removal is unnecessary (packet is not big TCP)
> + * Return error to indicate dropping the packet
> + */
> +static inline int ipv6_hopopt_jumbo_remove(struct sk_buff *skb)
> +{
> + const int hophdr_len = sizeof(struct hop_jumbo_hdr);
> + int nexthdr = ipv6_has_hopopt_jumbo(skb);
> + struct ipv6hdr *h6;
> + int err = 0;
> +
> + if (!nexthdr)
> + return err;
You can help a bit the compiler avoiding err initialization:
int err;
if (!nexthdr)
return 0;
> +
> + err = skb_cow_head(skb, 0);
> + if (err)
> + return err;
> +
> + /* Remove the HBH header.
> + * Layout: [Ethernet header][IPv6 header][HBH][L4 Header]
> + */
> + memmove(skb_mac_header(skb) + hophdr_len, skb_mac_header(skb),
> + skb_network_header(skb) - skb_mac_header(skb) +
The have could be:
skb_mac_header_len(skb)
which is IMHO a little more clear.
Thanks!
Paolo
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