From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: [net-next PATCH v2 4/8] udp: Do not pass checksum as a parameter to GSO segmentation Date: Fri, 04 May 2018 11:30:12 -0700 Message-ID: <20180504182958.5194.62398.stgit@localhost.localdomain> References: <20180504182537.5194.72775.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org, willemb@google.com, davem@davemloft.net Return-path: Received: from mail-io0-f194.google.com ([209.85.223.194]:41461 "EHLO mail-io0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751563AbeEDSaO (ORCPT ); Fri, 4 May 2018 14:30:14 -0400 Received: by mail-io0-f194.google.com with SMTP id e12-v6so26707579iob.8 for ; Fri, 04 May 2018 11:30:14 -0700 (PDT) In-Reply-To: <20180504182537.5194.72775.stgit@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: From: Alexander Duyck 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. If we cancel that out by adding the value XOR with 0xFFFF we can then just add the new length in and fold that into the new result. I think this may be fixing a checksum bug in the original code as well since the checksum that was passed included the UDP header in the checksum computation, but then excluded it for the adjustment on the last frame. I believe this may have an effect on things in the cases where the two differ by bits that would result in things crossing the byte boundaries. Signed-off-by: Alexander Duyck --- v2: New break-out patch based on one patch from earlier series include/net/udp.h | 3 +-- net/ipv4/udp_offload.c | 35 +++++++++++++++++++++-------------- net/ipv6/udp_offload.c | 7 +------ 3 files changed, 23 insertions(+), 22 deletions(-) diff --git a/include/net/udp.h b/include/net/udp.h index 8bd83b044ecd..9289b6425032 100644 --- a/include/net/udp.h +++ b/include/net/udp.h @@ -175,8 +175,7 @@ struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb, int udp_gro_complete(struct sk_buff *skb, int nhoff, udp_lookup_t lookup); struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, - netdev_features_t features, - __sum16 check); + netdev_features_t features); static inline struct udphdr *udp_gro_udphdr(struct sk_buff *skb) { diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index f21b63adcbbc..5c4bb8b9e83e 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -188,8 +188,7 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb, 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 sk_buff *seg, *segs = ERR_PTR(-EINVAL); struct sock *sk = gso_skb->sk; @@ -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) @@ -218,17 +219,28 @@ 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 = ~csum_fold((__force __wsum)((__force u32)uh->check + + ((__force u32)uh->len ^ 0xFFFF) + + (__force u32)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 = ~csum_fold((__force __wsum)((__force u32)uh->check + + ((__force u32)uh->len ^ 0xFFFF) + + (__force u32)newlen)); + } + + uh->len = newlen; + uh->check = check; - uh->check = ~uh->check; seg->destructor = sock_wfree; seg->sk = sk; sum_truesize += seg->truesize; @@ -243,15 +255,10 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, 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, diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c index dea03ec09715..61e34f1d2fa2 100644 --- a/net/ipv6/udp_offload.c +++ b/net/ipv6/udp_offload.c @@ -20,15 +20,10 @@ static struct sk_buff *__udp6_gso_segment(struct sk_buff *gso_skb, netdev_features_t features) { - const struct ipv6hdr *ip6h = ipv6_hdr(gso_skb); - unsigned int mss = skb_shinfo(gso_skb)->gso_size; - if (!can_checksum_protocol(features, htons(ETH_P_IPV6))) return ERR_PTR(-EIO); - return __udp_gso_segment(gso_skb, features, - udp_v6_check(sizeof(struct udphdr) + mss, - &ip6h->saddr, &ip6h->daddr, 0)); + return __udp_gso_segment(gso_skb, features); } static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,