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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>
This commit is contained in:
Paul Durrant 2013-10-16 17:50:29 +01:00 committed by David S. Miller
parent 146c8a77d2
commit 2eba61d55e
2 changed files with 222 additions and 56 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

269
drivers/net/xen-netback/netback.c
View File

@ -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)
{
@ -1118,14 +1115,214 @@ static int xenvif_set_skb_gso(struct xenvif *vif,
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 @@ static int checksum_setup(struct xenvif *vif, struct sk_buff *skb)
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 @@ 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));
}

9
drivers/net/xen-netback/xenbus.c
View File

@ -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);