Messages in this thread | | | From | Alexander Lobakin <> | Subject | Re: [PATCH net-next 1/2] IPv6/GRO: generic helper to remove temporary HBH/jumbo header in driver | Date | Wed, 23 Nov 2022 19:44:52 +0100 |
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From: Alexander Lobakin <alexandr.lobakin@intel.com> Date: Wed, 23 Nov 2022 17:38:25 +0100
> From: Coco Li <lixiaoyan@google.com> > Date: Tue, 22 Nov 2022 15:27:39 -0800 > > > 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@google.com> > > --- > > include/net/ipv6.h | 33 +++++++++++++++++++++++++++++++++ > > 1 file changed, 33 insertions(+) > > > > diff --git a/include/net/ipv6.h b/include/net/ipv6.h > > index d383c895592a..a11d58c85c05 100644 > > --- a/include/net/ipv6.h > > +++ b/include/net/ipv6.h > > @@ -500,6 +500,39 @@ 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; > > + > > + if (!nexthdr) > > + return 0; > > + > > + if (skb_cow_head(skb, 0)) > > + return -1; > > err = skb_cow_head(skb, 0); > if (err) > return err; > > Alternatively, if you want to keep it simple, make the function bool > and return false on `if (skb_cow_head(skb, 0)` and true otherwise. > > > + > > + /* Remove the HBH header. > > + * Layout: [Ethernet header][IPv6 header][HBH][L4 Header] > > + */ > > + memmove(skb->data + hophdr_len, > > + skb->data, > > This can fit into the previous line. > > > + ETH_HLEN + sizeof(struct ipv6hdr)); > > Not correct at this point. I assume you took the implementation from > ip6_offload.c[0], but ::gso_segment() and ::ndo_start_xmit() are two
Traditionally forgot to paste the links to the end of the mail. Pls look at the end of this one for them (if I don't forget to paste them again :clownface:).
> different entry points. Here you may have not only Eth header, but > also VLAN, MPLS and whatnot. > Correct way would be: > > memmove(skb_mac_header(skb) + hophdr_len, skb_mac_header(skb), > ipv6_hdr(skb) - skb_mac_header(skb) + > sizeof(struct ipv6hdr)); > > > + > > + skb->data += hophdr_len; > > + skb->len -= hophdr_len; > > + skb->network_header += hophdr_len; > > skb->mac_header also needs to be adjusted, the fact that it's equal > to skb->data at the entry of ::ndo_start_xmit() doesn't mean > anything.
Also, while I'm here: you should use skb_may_pull() + {,__}skb_pull() here instead of manual maths. ::network_header and ::mac_header still need to be adjusted manually tho.
> > > + > > + h6 = ipv6_hdr(skb); > > + h6->nexthdr = nexthdr; > > + > > + return 0; > > +} > > Please switch all the places where the same logics is used to your > new helper. > > > + > > static inline bool ipv6_accept_ra(struct inet6_dev *idev) > > { > > /* If forwarding is enabled, RA are not accepted unless the special > > -- > > 2.38.1.584.g0f3c55d4c2-goog > > Thanks, > Olek
[0] https://elixir.bootlin.com/linux/v6.1-rc6/source/net/ipv6/ip6_offload.c#L92
Thanks, Olek
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