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 <paul.durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index f3e591c..4271f8d1 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -109,15 +109,12 @@
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)
{
@@ -1118,14 +1115,214 @@
return 0;
}
+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 = (void *)skb->data;
+ unsigned int header_size;
+ unsigned int off;
+ int err = -EPROTO;
+
+ off = sizeof(struct iphdr);
+
+ header_size = skb->network_header + off + MAX_IPOPTLEN;
+ maybe_pull_tail(skb, header_size);
+
+ off = iph->ihl * 4;
+
+ switch (iph->protocol) {
+ 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_tcpudp_magic(iph->saddr, iph->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_tcpudp_magic(iph->saddr, iph->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",
+ iph->protocol);
+ goto out;
+ }
+
+ err = 0;
+
+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)
{
- struct iphdr *iph;
int err = -EPROTO;
int recalculate_partial_csum = 0;
- /*
- * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
+ /* 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.
@@ -1140,46 +1337,11 @@
if (skb->ip_summed != CHECKSUM_PARTIAL)
return 0;
- if (skb->protocol != htons(ETH_P_IP))
- goto out;
+ 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);
- iph = (void *)skb->data;
- switch (iph->protocol) {
- case IPPROTO_TCP:
- if (!skb_partial_csum_set(skb, 4 * iph->ihl,
- offsetof(struct tcphdr, check)))
- goto out;
-
- if (recalculate_partial_csum) {
- struct tcphdr *tcph = tcp_hdr(skb);
- tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
- skb->len - iph->ihl*4,
- IPPROTO_TCP, 0);
- }
- break;
- case IPPROTO_UDP:
- if (!skb_partial_csum_set(skb, 4 * iph->ihl,
- offsetof(struct udphdr, check)))
- goto out;
-
- if (recalculate_partial_csum) {
- struct udphdr *udph = udp_hdr(skb);
- udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
- skb->len - iph->ihl*4,
- 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",
- iph->protocol);
- goto out;
- }
-
- err = 0;
-
-out:
return err;
}
@@ -1428,12 +1590,7 @@
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 ad27b15..108e752 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -105,6 +105,15 @@
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);