On Fri, May 4, 2018 at 8:30 PM, Alexander Duyck
<alexander.du...@gmail.com> wrote:
> From: Alexander Duyck <alexander.h.du...@intel.com>
>
> This patch allows us to take care of unrolling the first segment and the
> last segment
Only the last segment needs to be unrolled, right?
> of the loop for processing the segmented skb. Part of the
> motivation for this is that it makes it easier to process the fact that the
> first fame and all of the frames in between should be mostly identical
> in terms of header data, and the last frame has differences in the length
> and partial checksum.
>
> In addition I am dropping the header length calculation since we don't
> really need it for anything but the last frame and it can be easily
> obtained by just pulling the data_len and offset of tail from the transport
> header.
>
> Signed-off-by: Alexander Duyck <alexander.h.du...@intel.com>
> ---
>
> v2: New break-out patch based on one patch from earlier series
>
> net/ipv4/udp_offload.c | 35 ++++++++++++++++++++---------------
> 1 file changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 5c4bb8b9e83e..946d06d2aa0c 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -193,7 +193,6 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> struct sk_buff *seg, *segs = ERR_PTR(-EINVAL);
> struct sock *sk = gso_skb->sk;
> unsigned int sum_truesize = 0;
> - unsigned int hdrlen;
> struct udphdr *uh;
> unsigned int mss;
> __sum16 check;
> @@ -206,7 +205,6 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> if (!pskb_may_pull(gso_skb, sizeof(*uh)))
> goto out;
>
> - hdrlen = gso_skb->data - skb_mac_header(gso_skb);
> skb_pull(gso_skb, sizeof(*uh));
>
> /* clear destructor to avoid skb_segment assigning it to tail */
> @@ -219,7 +217,8 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> return segs;
> }
>
> - uh = udp_hdr(segs);
> + seg = segs;
> + uh = udp_hdr(seg);
>
> /* compute checksum adjustment based on old length versus new */
> newlen = htons(sizeof(*uh) + mss);
> @@ -227,25 +226,31 @@ struct sk_buff *__udp_gso_segment(struct sk_buff
> *gso_skb,
> ((__force u32)uh->len ^ 0xFFFF) +
> (__force u32)newlen));
>
> - for (seg = segs; seg; seg = seg->next) {
> - uh = udp_hdr(seg);
> + for (;;) {
> + seg->destructor = sock_wfree;
> + seg->sk = sk;
> + sum_truesize += seg->truesize;
>
> - /* last packet can be partial gso_size */
> - if (!seg->next) {
> - newlen = htons(seg->len - hdrlen);
> - check = ~csum_fold((__force __wsum)((__force
> u32)uh->check +
> - ((__force
> u32)uh->len ^ 0xFFFF) +
> - (__force
> u32)newlen));
> - }
> + if (!seg->next)
> + break;
Not critical, but I find replacing
for (seg = segs; seg; seg = seg->next) {
uh = udp_hdr(seg);
...
}
with
uh = udp_hdr(seg);
for (;;) {
...
if (!seg->next)
break;
uh = udp_hdr(seg);
}
much less easy to parse and it inflates patch size. How about just
- for (seg = segs; seg; seg = seg->next)
+ for( seg = segs; seg->next; seg = seg->next)
>
> uh->len = newlen;
> uh->check = check;
>
> - seg->destructor = sock_wfree;
> - seg->sk = sk;
> - sum_truesize += seg->truesize;
> + seg = seg->next;
> + uh = udp_hdr(seg);
> }
>
> + /* last packet can be partial gso_size, account for that in checksum
> */
> + newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
> + seg->data_len);
> + check = ~csum_fold((__force __wsum)((__force u32)uh->check +
> + ((__force u32)uh->len ^ 0xFFFF) +
> + (__force u32)newlen));
> + uh->len = newlen;
> + uh->check = check;
> +
> + /* update refcount for the packet */
> refcount_add(sum_truesize - gso_skb->truesize, &sk->sk_wmem_alloc);
> out:
> return segs;
>
