The Linux network stack expects all GSO SKBs to have ip_summed ==
CHECKSUM_PARTIAL (which implies that the frame contains a partial
checksum) and the Xen network ring protocol similarly expects an SKB
which has GSO set to also have NETRX_csum_blank (which also implies a
partial checksum).
However there have been cases of buggy guests which mark a frame as
GSO but do not set csum_blank. If we detect that we a receiving such a
frame (which manifests as ip_summed != PARTIAL && skb_is_gso) then
force the SKB to partial and recalculate the checksum, since we cannot
rely on the peer having done so if they have not set csum_blank.
Add an ethtool stat to track occurances of this event.
Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
---
drivers/net/xen-netfront.c | 96 ++++++++++++++++++++++++++++++++++++++++----
1 files changed, 88 insertions(+), 8 deletions(-)
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 546de57..da1f121 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -120,6 +120,9 @@ struct netfront_info {
unsigned long rx_pfn_array[NET_RX_RING_SIZE];
struct multicall_entry rx_mcl[NET_RX_RING_SIZE+1];
struct mmu_update rx_mmu[NET_RX_RING_SIZE];
+
+ /* Statistics */
+ int rx_gso_checksum_fixup;
};
struct netfront_rx_info {
@@ -770,11 +773,29 @@ static RING_IDX xennet_fill_frags(struct netfront_info
*np,
return cons;
}
-static int skb_checksum_setup(struct sk_buff *skb)
+static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
{
struct iphdr *iph;
unsigned char *th;
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)) {
+ struct netfront_info *np = netdev_priv(dev);
+ np->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))
goto out;
@@ -788,9 +809,23 @@ static int skb_checksum_setup(struct sk_buff *skb)
switch (iph->protocol) {
case IPPROTO_TCP:
skb->csum_offset = offsetof(struct tcphdr, check);
+
+ if (recalculate_partial_csum) {
+ struct tcphdr *tcph = (struct tcphdr *)th;
+ tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
+ skb->len - iph->ihl*4,
+ IPPROTO_TCP, 0);
+ }
break;
case IPPROTO_UDP:
skb->csum_offset = offsetof(struct udphdr, check);
+
+ if (recalculate_partial_csum) {
+ struct udphdr *udph = (struct udphdr *)th;
+ udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
+ skb->len - iph->ihl*4,
+ IPPROTO_UDP, 0);
+ }
break;
default:
if (net_ratelimit())
@@ -829,13 +864,11 @@ static int handle_incoming_queue(struct net_device *dev,
/* Ethernet work: Delayed to here as it peeks the header. */
skb->protocol = eth_type_trans(skb, dev);
- if (skb->ip_summed == CHECKSUM_PARTIAL) {
- if (skb_checksum_setup(skb)) {
- kfree_skb(skb);
- packets_dropped++;
- dev->stats.rx_errors++;
- continue;
- }
+ if (checksum_setup(dev, skb)) {
+ kfree_skb(skb);
+ packets_dropped++;
+ dev->stats.rx_errors++;
+ continue;
}
dev->stats.rx_packets++;
@@ -1632,12 +1665,59 @@ static void netback_changed(struct xenbus_device *dev,
}
}
+static const struct xennet_stat {
+ char name[ETH_GSTRING_LEN];
+ u16 offset;
+} xennet_stats[] = {
+ {
+ "rx_gso_checksum_fixup",
+ offsetof(struct netfront_info, rx_gso_checksum_fixup)
+ },
+};
+
+static int xennet_get_sset_count(struct net_device *dev, int string_set)
+{
+ switch (string_set) {
+ case ETH_SS_STATS:
+ return ARRAY_SIZE(xennet_stats);
+ default:
+ return -EINVAL;
+ }
+}
+
+static void xennet_get_ethtool_stats(struct net_device *dev,
+ struct ethtool_stats *stats, u64 * data)
+{
+ void *np = netdev_priv(dev);
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(xennet_stats); i++)
+ data[i] = *(int *)(np + xennet_stats[i].offset);
+}
+
+static void xennet_get_strings(struct net_device *dev, u32 stringset, u8 *
data)
+{
+ int i;
+
+ switch (stringset) {
+ case ETH_SS_STATS:
+ for (i = 0; i < ARRAY_SIZE(xennet_stats); i++)
+ memcpy(data + i * ETH_GSTRING_LEN,
+ xennet_stats[i].name, ETH_GSTRING_LEN);
+ break;
+ }
+}
+
static const struct ethtool_ops xennet_ethtool_ops =
{
.set_tx_csum = ethtool_op_set_tx_csum,
.set_sg = xennet_set_sg,
.set_tso = xennet_set_tso,
.get_link = ethtool_op_get_link,
+
+ .get_sset_count = xennet_get_sset_count,
+ .get_ethtool_stats = xennet_get_ethtool_stats,
+ .get_strings = xennet_get_strings,
};
#ifdef CONFIG_SYSFS
--
1.5.6.5
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