net: Add debug info to track down GSO checksum bug

I'm trying to track down why people're hitting the checksum warning
in skb_gso_segment.  As the problem seems to be hitting lots of
people and I can't reproduce it or locate the bug, here is a patch
to print out more details which hopefully should help us to track
this down.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 8d675975d85b..6e44c3277101 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1534,7 +1534,19 @@ struct sk_buff *skb_gso_segment(struct sk_buff *skb, int features)
         skb->mac_len = skb->network_header - skb->mac_header;
         __skb_pull(skb, skb->mac_len);
 
-        if (WARN_ON(skb->ip_summed != CHECKSUM_PARTIAL)) {
+        if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
+                struct net_device *dev = skb->dev;
+                struct ethtool_drvinfo info = {};
+
+                if (dev && dev->ethtool_ops && dev->ethtool_ops->get_drvinfo)
+                        dev->ethtool_ops->get_drvinfo(dev, &info);
+
+                WARN(1, "%s: caps=(0x%lx, 0x%lx) len=%d data_len=%d "
+                        "ip_summed=%d",
+                     info.driver, dev ? dev->features : 0L,
+                     skb->sk ? skb->sk->sk_route_caps : 0L,
+                     skb->len, skb->data_len, skb->ip_summed);
+
                 if (skb_header_cloned(skb) &&
                     (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
                         return ERR_PTR(err);