From 9a0d41b3598ff62ecb26661bbfb1d523586cdea3 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Mon, 7 May 2018 11:08:34 -0700 Subject: udp: Do not pass checksum as a parameter to GSO segmentation This patch is meant to allow us to avoid having to recompute the checksum from scratch and have it passed as a parameter. Instead of taking that approach we can take advantage of the fact that the length that was used to compute the existing checksum is included in the UDP header. Finally to avoid the need to invert the result we can just call csum16_add and csum16_sub directly. By doing this we can avoid a number of instructions in the loop that is handling segmentation. Signed-off-by: Alexander Duyck Acked-by: Willem de Bruijn Signed-off-by: David S. Miller --- net/ipv4/udp_offload.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) (limited to 'net/ipv4/udp_offload.c') diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index c1afcd2f1a76..92c182e99ddc 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -188,8 +188,7 @@ out_unlock: EXPORT_SYMBOL(skb_udp_tunnel_segment); struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, - netdev_features_t features, - __sum16 check) + netdev_features_t features) { struct sock *sk = gso_skb->sk; unsigned int sum_truesize = 0; @@ -197,6 +196,8 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, unsigned int hdrlen; struct udphdr *uh; unsigned int mss; + __sum16 check; + __be16 newlen; mss = skb_shinfo(gso_skb)->gso_size; if (gso_skb->len <= sizeof(*uh) + mss) @@ -215,17 +216,25 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, return segs; } + uh = udp_hdr(segs); + + /* compute checksum adjustment based on old length versus new */ + newlen = htons(sizeof(*uh) + mss); + check = csum16_add(csum16_sub(uh->check, uh->len), newlen); + for (seg = segs; seg; seg = seg->next) { uh = udp_hdr(seg); - uh->len = htons(seg->len - hdrlen); - uh->check = check; /* last packet can be partial gso_size */ - if (!seg->next) - csum_replace2(&uh->check, htons(mss), - htons(seg->len - hdrlen - sizeof(*uh))); + if (!seg->next) { + newlen = htons(seg->len - hdrlen); + check = csum16_add(csum16_sub(uh->check, uh->len), + newlen); + } + + uh->len = newlen; + uh->check = check; - uh->check = ~uh->check; seg->destructor = sock_wfree; seg->sk = sk; sum_truesize += seg->truesize; @@ -240,15 +249,10 @@ EXPORT_SYMBOL_GPL(__udp_gso_segment); static struct sk_buff *__udp4_gso_segment(struct sk_buff *gso_skb, netdev_features_t features) { - const struct iphdr *iph = ip_hdr(gso_skb); - unsigned int mss = skb_shinfo(gso_skb)->gso_size; - if (!can_checksum_protocol(features, htons(ETH_P_IP))) return ERR_PTR(-EIO); - return __udp_gso_segment(gso_skb, features, - udp_v4_check(sizeof(struct udphdr) + mss, - iph->saddr, iph->daddr, 0)); + return __udp_gso_segment(gso_skb, features); } static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb, -- cgit v1.2.3