net: Support for csum_bad in skbuff

This flag indicates that an invalid checksum was detected in the
packet. __skb_mark_checksum_bad helper function was added to set this.

Checksums can be marked bad from a driver or the GRO path (the latter
is implemented in this patch). csum_bad is checked in
__skb_checksum_validate_complete (i.e. calling that when ip_summed ==
CHECKSUM_NONE).

csum_bad works in conjunction with ip_summed value. In the case that
ip_summed is CHECKSUM_NONE and csum_bad is set, this implies that the
first (or next) checksum encountered in the packet is bad. When
ip_summed is CHECKSUM_UNNECESSARY, the first checksum after the last
one validated is bad. For example, if ip_summed == CHECKSUM_UNNECESSARY,
csum_level == 1, and csum_bad is set-- then the third checksum in the
packet is bad. In the normal path, the packet will be dropped when
processing the protocol layer of the bad checksum:
__skb_decr_checksum_unnecessary called twice for the good checksums
changing ip_summed to CHECKSUM_NONE so that
__skb_checksum_validate_complete is called to validate the third
checksum and that will fail since csum_bad is set.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 202c25a9aadf5ab7fa371a379470af9d0082343d..a0ab6d9d400aabb86e65501ae984174b4db89859 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2216,7 +2216,9 @@ static inline void skb_gro_incr_csum_unnecessary(struct sk_buff *skb)
        if (__skb_gro_checksum_validate_needed(skb, zero_okay, check))  \
                __ret = __skb_gro_checksum_validate_complete(skb,       \
                                compute_pseudo(skb, proto));            \
-       if (!__ret)                                                     \
+       if (__ret)                                                      \
+               __skb_mark_checksum_bad(skb);                           \
+       else                                                            \
                skb_gro_incr_csum_unnecessary(skb);                     \
        __ret;                                                          \
 })

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c93b5859a772b9dd58eab291892af34e1da8fd07..23710a243439b19e1c21fec09ba5ed55522198cf 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -617,7 +617,8 @@ struct sk_buff {
 
        kmemcheck_bitfield_begin(flags3);
        __u8                    csum_level:2;
-       /* 14 bit hole */
+       __u8                    csum_bad:1;
+       /* 13 bit hole */
        kmemcheck_bitfield_end(flags3);
 
        __be16                  inner_protocol;
@@ -2825,6 +2826,21 @@ static inline void __skb_incr_checksum_unnecessary(struct sk_buff *skb)
        }
 }
 
+static inline void __skb_mark_checksum_bad(struct sk_buff *skb)
+{
+       /* Mark current checksum as bad (typically called from GRO
+        * path). In the case that ip_summed is CHECKSUM_NONE
+        * this must be the first checksum encountered in the packet.
+        * When ip_summed is CHECKSUM_UNNECESSARY, this is the first
+        * checksum after the last one validated. For UDP, a zero
+        * checksum can not be marked as bad.
+        */
+
+       if (skb->ip_summed == CHECKSUM_NONE ||
+           skb->ip_summed == CHECKSUM_UNNECESSARY)
+               skb->csum_bad = 1;
+}
+
 /* Check if we need to perform checksum complete validation.
  *
  * Returns true if checksum complete is needed, false otherwise
@@ -2866,6 +2882,9 @@ static inline __sum16 __skb_checksum_validate_complete(struct sk_buff *skb,
                        skb->csum_valid = 1;
                        return 0;
                }
+       } else if (skb->csum_bad) {
+               /* ip_summed == CHECKSUM_NONE in this case */
+               return 1;
        }
 
        skb->csum = psum;

diff --git a/net/core/dev.c b/net/core/dev.c
index 6857d57aa294f043b9f58b739ce5e14c849c3902..3774afc3bebfa71cb7ff1513843568f4551530db 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3918,7 +3918,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
        if (!(skb->dev->features & NETIF_F_GRO))
                goto normal;
 
-       if (skb_is_gso(skb) || skb_has_frag_list(skb))
+       if (skb_is_gso(skb) || skb_has_frag_list(skb) || skb->csum_bad)
                goto normal;
 
        gro_list_prepare(napi, skb);