From 2eba61d55e5104d0bf08ba4a9cc609613f52b4c9 Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Wed, 16 Oct 2013 17:50:29 +0100 Subject: [PATCH] xen-netback: add support for IPv6 checksum offload from guest For performance of VM to VM traffic on a single host it is better to avoid calculation of TCP/UDP checksum in the sending frontend. To allow this this patch adds the code necessary to set up partial checksum for IPv6 packets and xenstore flag feature-ipv6-csum-offload to advertise that fact to frontends. Signed-off-by: Paul Durrant Cc: Wei Liu Cc: David Vrabel Cc: Ian Campbell Signed-off-by: David S. Miller --- drivers/net/xen-netback/netback.c | 235 +++++++++++++++++++++++++----- drivers/net/xen-netback/xenbus.c | 9 ++ 2 files changed, 205 insertions(+), 39 deletions(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index f3e591c611de..4271f8d1da7a 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -109,15 +109,12 @@ static inline unsigned long idx_to_kaddr(struct xenvif *vif, return (unsigned long)pfn_to_kaddr(idx_to_pfn(vif, idx)); } -/* - * This is the amount of packet we copy rather than map, so that the - * guest can't fiddle with the contents of the headers while we do - * packet processing on them (netfilter, routing, etc). +/* This is a miniumum size for the linear area to avoid lots of + * calls to __pskb_pull_tail() as we set up checksum offsets. The + * value 128 was chosen as it covers all IPv4 and most likely + * IPv6 headers. */ -#define PKT_PROT_LEN (ETH_HLEN + \ - VLAN_HLEN + \ - sizeof(struct iphdr) + MAX_IPOPTLEN + \ - sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE) +#define PKT_PROT_LEN 128 static u16 frag_get_pending_idx(skb_frag_t *frag) { @@ -1118,61 +1115,74 @@ static int xenvif_set_skb_gso(struct xenvif *vif, return 0; } -static int checksum_setup(struct xenvif *vif, struct sk_buff *skb) +static inline void maybe_pull_tail(struct sk_buff *skb, unsigned int len) +{ + if (skb_is_nonlinear(skb) && skb_headlen(skb) < len) { + /* If we need to pullup then pullup to the max, so we + * won't need to do it again. + */ + int target = min_t(int, skb->len, MAX_TCP_HEADER); + __pskb_pull_tail(skb, target - skb_headlen(skb)); + } +} + +static int checksum_setup_ip(struct xenvif *vif, struct sk_buff *skb, + int recalculate_partial_csum) { - struct iphdr *iph; + struct iphdr *iph = (void *)skb->data; + unsigned int header_size; + unsigned int off; int err = -EPROTO; - int recalculate_partial_csum = 0; - /* - * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy - * peers can fail to set NETRXF_csum_blank when sending a GSO - * frame. In this case force the SKB to CHECKSUM_PARTIAL and - * recalculate the partial checksum. - */ - if (skb->ip_summed != CHECKSUM_PARTIAL && skb_is_gso(skb)) { - vif->rx_gso_checksum_fixup++; - skb->ip_summed = CHECKSUM_PARTIAL; - recalculate_partial_csum = 1; - } + off = sizeof(struct iphdr); - /* A non-CHECKSUM_PARTIAL SKB does not require setup. */ - if (skb->ip_summed != CHECKSUM_PARTIAL) - return 0; + header_size = skb->network_header + off + MAX_IPOPTLEN; + maybe_pull_tail(skb, header_size); - if (skb->protocol != htons(ETH_P_IP)) - goto out; + off = iph->ihl * 4; - iph = (void *)skb->data; switch (iph->protocol) { case IPPROTO_TCP: - if (!skb_partial_csum_set(skb, 4 * iph->ihl, + if (!skb_partial_csum_set(skb, off, offsetof(struct tcphdr, check))) goto out; if (recalculate_partial_csum) { struct tcphdr *tcph = tcp_hdr(skb); + + header_size = skb->network_header + + off + + sizeof(struct tcphdr); + maybe_pull_tail(skb, header_size); + tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, - skb->len - iph->ihl*4, + skb->len - off, IPPROTO_TCP, 0); } break; case IPPROTO_UDP: - if (!skb_partial_csum_set(skb, 4 * iph->ihl, + if (!skb_partial_csum_set(skb, off, offsetof(struct udphdr, check))) goto out; if (recalculate_partial_csum) { struct udphdr *udph = udp_hdr(skb); + + header_size = skb->network_header + + off + + sizeof(struct udphdr); + maybe_pull_tail(skb, header_size); + udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, - skb->len - iph->ihl*4, + skb->len - off, IPPROTO_UDP, 0); } break; default: if (net_ratelimit()) netdev_err(vif->dev, - "Attempting to checksum a non-TCP/UDP packet, dropping a protocol %d packet\n", + "Attempting to checksum a non-TCP/UDP packet, " + "dropping a protocol %d packet\n", iph->protocol); goto out; } @@ -1183,6 +1193,158 @@ out: return err; } +static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb, + int recalculate_partial_csum) +{ + int err = -EPROTO; + struct ipv6hdr *ipv6h = (void *)skb->data; + u8 nexthdr; + unsigned int header_size; + unsigned int off; + bool fragment; + bool done; + + done = false; + + off = sizeof(struct ipv6hdr); + + header_size = skb->network_header + off; + maybe_pull_tail(skb, header_size); + + nexthdr = ipv6h->nexthdr; + + while ((off <= sizeof(struct ipv6hdr) + ntohs(ipv6h->payload_len)) && + !done) { + switch (nexthdr) { + case IPPROTO_DSTOPTS: + case IPPROTO_HOPOPTS: + case IPPROTO_ROUTING: { + struct ipv6_opt_hdr *hp = (void *)(skb->data + off); + + header_size = skb->network_header + + off + + sizeof(struct ipv6_opt_hdr); + maybe_pull_tail(skb, header_size); + + nexthdr = hp->nexthdr; + off += ipv6_optlen(hp); + break; + } + case IPPROTO_AH: { + struct ip_auth_hdr *hp = (void *)(skb->data + off); + + header_size = skb->network_header + + off + + sizeof(struct ip_auth_hdr); + maybe_pull_tail(skb, header_size); + + nexthdr = hp->nexthdr; + off += (hp->hdrlen+2)<<2; + break; + } + case IPPROTO_FRAGMENT: + fragment = true; + /* fall through */ + default: + done = true; + break; + } + } + + if (!done) { + if (net_ratelimit()) + netdev_err(vif->dev, "Failed to parse packet header\n"); + goto out; + } + + if (fragment) { + if (net_ratelimit()) + netdev_err(vif->dev, "Packet is a fragment!\n"); + goto out; + } + + switch (nexthdr) { + case IPPROTO_TCP: + if (!skb_partial_csum_set(skb, off, + offsetof(struct tcphdr, check))) + goto out; + + if (recalculate_partial_csum) { + struct tcphdr *tcph = tcp_hdr(skb); + + header_size = skb->network_header + + off + + sizeof(struct tcphdr); + maybe_pull_tail(skb, header_size); + + tcph->check = ~csum_ipv6_magic(&ipv6h->saddr, + &ipv6h->daddr, + skb->len - off, + IPPROTO_TCP, 0); + } + break; + case IPPROTO_UDP: + if (!skb_partial_csum_set(skb, off, + offsetof(struct udphdr, check))) + goto out; + + if (recalculate_partial_csum) { + struct udphdr *udph = udp_hdr(skb); + + header_size = skb->network_header + + off + + sizeof(struct udphdr); + maybe_pull_tail(skb, header_size); + + udph->check = ~csum_ipv6_magic(&ipv6h->saddr, + &ipv6h->daddr, + skb->len - off, + IPPROTO_UDP, 0); + } + break; + default: + if (net_ratelimit()) + netdev_err(vif->dev, + "Attempting to checksum a non-TCP/UDP packet, " + "dropping a protocol %d packet\n", + nexthdr); + goto out; + } + + err = 0; + +out: + return err; +} + +static int checksum_setup(struct xenvif *vif, struct sk_buff *skb) +{ + int err = -EPROTO; + int recalculate_partial_csum = 0; + + /* A GSO SKB must be CHECKSUM_PARTIAL. However some buggy + * peers can fail to set NETRXF_csum_blank when sending a GSO + * frame. In this case force the SKB to CHECKSUM_PARTIAL and + * recalculate the partial checksum. + */ + if (skb->ip_summed != CHECKSUM_PARTIAL && skb_is_gso(skb)) { + vif->rx_gso_checksum_fixup++; + skb->ip_summed = CHECKSUM_PARTIAL; + recalculate_partial_csum = 1; + } + + /* A non-CHECKSUM_PARTIAL SKB does not require setup. */ + if (skb->ip_summed != CHECKSUM_PARTIAL) + return 0; + + if (skb->protocol == htons(ETH_P_IP)) + err = checksum_setup_ip(vif, skb, recalculate_partial_csum); + else if (skb->protocol == htons(ETH_P_IPV6)) + err = checksum_setup_ipv6(vif, skb, recalculate_partial_csum); + + return err; +} + static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) { unsigned long now = jiffies; @@ -1428,12 +1590,7 @@ static int xenvif_tx_submit(struct xenvif *vif, int budget) xenvif_fill_frags(vif, skb); - /* - * If the initial fragment was < PKT_PROT_LEN then - * pull through some bytes from the other fragments to - * increase the linear region to PKT_PROT_LEN bytes. - */ - if (skb_headlen(skb) < PKT_PROT_LEN && skb_is_nonlinear(skb)) { + if (skb_is_nonlinear(skb) && skb_headlen(skb) < PKT_PROT_LEN) { int target = min_t(int, skb->len, PKT_PROT_LEN); __pskb_pull_tail(skb, target - skb_headlen(skb)); } diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index ad27b15242cd..108e7523017a 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -105,6 +105,15 @@ static int netback_probe(struct xenbus_device *dev, goto abort_transaction; } + /* We support partial checksum setup for IPv6 packets */ + err = xenbus_printf(xbt, dev->nodename, + "feature-ipv6-csum-offload", + "%d", 1); + if (err) { + message = "writing feature-ipv6-csum-offload"; + goto abort_transaction; + } + /* We support rx-copy path. */ err = xenbus_printf(xbt, dev->nodename, "feature-rx-copy", "%d", 1); -- 2.20.1