diff mbox series

[net-next,v2,1/2] IPv6/GRO: generic helper to remove temporary HBH/jumbo header in driver

Message ID 20221123191627.3442831-1-lixiaoyan@google.com
State New
Headers
Series [net-next,v2,1/2] IPv6/GRO: generic helper to remove temporary HBH/jumbo header in driver |

Commit Message

Coco Li Nov. 23, 2022, 7:16 p.m. UTC 
  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     | 36 ++++++++++++++++++++++++++++++++++++
 net/ipv6/ip6_offload.c | 26 ++++----------------------
 2 files changed, 40 insertions(+), 22 deletions(-)

Comments

Paolo Abeni Nov. 29, 2022, 9:33 a.m. UTC | #1 
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@google.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
Alexander Lobakin Nov. 29, 2022, 1:41 p.m. UTC | #2 
From: Paolo Abeni <pabeni@redhat.com>
Date: Tue, 29 Nov 2022 10:33:59 +0100

> 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:

[...]

> > +static inline int ipv6_hopopt_jumbo_remove(struct sk_buff *skb)

I thinks it's relatively small and inlineable enough to not make it
an external function, right? I'd keep it inline just how the author
does it, the compiler then will decide.

> > +{
> > +	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;

Same with the end of the function, @err is unused after
skb_cow_head() and always equal 0, so the end return could be just
`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

Thanks,
Olek
diff mbox series

Patch

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;
+
+	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) +
+		sizeof(struct ipv6hdr));
+
+	skb->data += hophdr_len;
+	skb->len -= hophdr_len;
+	skb->network_header += hophdr_len;
+	skb->mac_header += hophdr_len;
+
+	h6 = ipv6_hdr(skb);
+	h6->nexthdr = nexthdr;
+
+	return err;
+}
+
 static inline bool ipv6_accept_ra(struct inet6_dev *idev)
 {
 	/* If forwarding is enabled, RA are not accepted unless the special
diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 3ee345672849..60a82342fe57 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -77,7 +77,7 @@  static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	struct ipv6hdr *ipv6h;
 	const struct net_offload *ops;
-	int proto, nexthdr;
+	int proto, err;
 	struct frag_hdr *fptr;
 	unsigned int payload_len;
 	u8 *prevhdr;
@@ -87,28 +87,10 @@  static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	bool gso_partial;
 
 	skb_reset_network_header(skb);
-	nexthdr = ipv6_has_hopopt_jumbo(skb);
-	if (nexthdr) {
-		const int hophdr_len = sizeof(struct hop_jumbo_hdr);
-		int err;
+	err = ipv6_hopopt_jumbo_remove(skb);
+	if (err)
+		return ERR_PTR(err);
 
-		err = skb_cow_head(skb, 0);
-		if (err < 0)
-			return ERR_PTR(err);
-
-		/* remove the HBH header.
-		 * Layout: [Ethernet header][IPv6 header][HBH][TCP header]
-		 */
-		memmove(skb_mac_header(skb) + hophdr_len,
-			skb_mac_header(skb),
-			ETH_HLEN + sizeof(struct ipv6hdr));
-		skb->data += hophdr_len;
-		skb->len -= hophdr_len;
-		skb->network_header += hophdr_len;
-		skb->mac_header += hophdr_len;
-		ipv6h = (struct ipv6hdr *)skb->data;
-		ipv6h->nexthdr = nexthdr;
-	}
 	nhoff = skb_network_header(skb) - skb_mac_header(skb);
 	if (unlikely(!pskb_may_pull(skb, sizeof(*ipv6h))))
 		goto out;