On Fri, Feb 5, 2016 at 3:28 PM, Alexander Duyck <adu...@mirantis.com> wrote:
> The segmentation code was having to do a bunch of work to pull the
> skb->len and strip the udp header offset before the value could be used to
> adjust the checksum. Instead of doing all this work we can just use the
> value that goes into uh->len since that is the correct value with the
> correct byte order that we need anyway. By using this value we can save
> ourselves a bunch of pain as there is no need to do multiple byte swaps.
>
> Signed-off-by: Alexander Duyck <adu...@mirantis.com>
Acked-by: Tom Herbert <t...@herbertland.com>
> ---
> net/ipv4/udp_offload.c | 28 +++++++++++++---------------
> 1 file changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 9e4816fc9927..56c4c8b88b28 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -32,20 +32,23 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct
> sk_buff *skb,
> netdev_features_t features),
> __be16 new_protocol, bool is_ipv6)
> {
> + int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
> struct sk_buff *segs = ERR_PTR(-EINVAL);
> bool remcsum, need_csum, offload_csum;
> + struct udphdr *uh = udp_hdr(skb);
> u16 mac_offset = skb->mac_header;
> - int mac_len = skb->mac_len;
> - int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
> __be16 protocol = skb->protocol;
> + u16 mac_len = skb->mac_len;
> int udp_offset, outer_hlen;
> - unsigned int oldlen;
> -
> - oldlen = (u16)~skb->len;
> + u32 partial;
>
> if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
> goto out;
>
> + /* adjust partial header checksum to negate old length */
> + partial = (__force u32)uh->check + (__force u16)~uh->len;
> +
> + /* setup inner skb. */
> skb->encapsulation = 0;
> __skb_pull(skb, tnl_hlen);
> skb_reset_mac_header(skb);
> @@ -89,9 +92,7 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct
> sk_buff *skb,
> udp_offset = outer_hlen - tnl_hlen;
> skb = segs;
> do {
> - struct udphdr *uh;
> - int len;
> - __be32 delta;
> + __be16 len;
>
> if (remcsum)
> skb->ip_summed = CHECKSUM_NONE;
> @@ -105,22 +106,19 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct
> sk_buff *skb,
> skb->mac_len = mac_len;
> skb->protocol = protocol;
>
> - skb_push(skb, outer_hlen);
> + __skb_push(skb, outer_hlen);
> skb_reset_mac_header(skb);
> skb_set_network_header(skb, mac_len);
> skb_set_transport_header(skb, udp_offset);
> - len = skb->len - udp_offset;
> + len = htons(skb->len - udp_offset);
> uh = udp_hdr(skb);
> - uh->len = htons(len);
> + uh->len = len;
>
> if (!need_csum)
> continue;
>
> - delta = htonl(oldlen + len);
> -
> uh->check = ~csum_fold((__force __wsum)
> - ((__force u32)uh->check +
> - (__force u32)delta));
> + ((__force u32)len + partial));
>
> if (skb->encapsulation || !offload_csum) {
> uh->check = gso_make_checksum(skb, ~uh->check);
>
