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Date: Tue, 8 Oct 2013 11:58:13 +0100
From: Paul Durrant <paul.durrant@...rix.com>
To: <xen-devel@...ts.xen.org>, <netdev@...r.kernel.org>
CC: Paul Durrant <paul.durrant@...rix.com>,
Wei Liu <wei.liu2@...rix.com>,
David Vrabel <david.vrabel@...rix.com>,
Ian Campbell <ian.campbell@...rix.com>
Subject: [PATCH net-next v2 2/5] 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@...rix.com>
Cc: Wei Liu <wei.liu2@...rix.com>
Cc: David Vrabel <david.vrabel@...rix.com>
Cc: Ian Campbell <ian.campbell@...rix.com>
---
drivers/net/xen-netback/netback.c | 224 ++++++++++++++++++++++++++++++-------
drivers/net/xen-netback/xenbus.c | 9 ++
2 files changed, 191 insertions(+), 42 deletions(-)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index f3e591c..35b1fa6 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -109,15 +109,10 @@ 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.
*/
-#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 +1113,72 @@ 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)
{
- struct iphdr *iph;
+ if (skb_is_nonlinear(skb) && skb_headlen(skb) < len) {
+ int target = min_t(int, skb->len, len);
+ __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;
- 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) +
+ MAX_TCP_OPTION_SPACE;
+ 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 +1189,148 @@ 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 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) {
+ /* We only access at most the first 2 bytes of any option header
+ * to determine the next one.
+ */
+ header_size = skb->network_header + off + 2;
+ maybe_pull_tail(skb, header_size);
+
+ switch (nexthdr) {
+ case IPPROTO_FRAGMENT: {
+ struct frag_hdr *hp = (void *)(skb->data + off);
+
+ nexthdr = hp->nexthdr;
+ off += 8;
+ break;
+ }
+ case IPPROTO_DSTOPTS:
+ case IPPROTO_HOPOPTS:
+ case IPPROTO_ROUTING: {
+ struct ipv6_opt_hdr *hp = (void *)(skb->data + off);
+
+ nexthdr = hp->nexthdr;
+ off += ipv6_optlen(hp);
+ break;
+ }
+ case IPPROTO_AH: {
+ struct ip_auth_hdr *hp = (void *)(skb->data + off);
+
+ nexthdr = hp->nexthdr;
+ off += (hp->hdrlen+2)<<2;
+ break;
+ }
+ default:
+ done = true;
+ break;
+ }
+ }
+
+ if (!done)
+ 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) +
+ MAX_TCP_OPTION_SPACE;
+ 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;
@@ -1428,15 +1576,7 @@ 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)) {
- int target = min_t(int, skb->len, PKT_PROT_LEN);
- __pskb_pull_tail(skb, target - skb_headlen(skb));
- }
+ maybe_pull_tail(skb, PKT_PROT_LEN);
skb->dev = vif->dev;
skb->protocol = eth_type_trans(skb, skb->dev);
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 5e45b00..dff423b 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -101,6 +101,15 @@ 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);
--
1.7.10.4
--
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