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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>
This commit is contained in:
Tom Herbert 2014-08-31 15:12:41 -07:00 committed by David S. Miller
parent 52aec126c4
commit 5a21232983
3 changed files with 24 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/netdevice.h
View File

@ -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; \
})

21
include/linux/skbuff.h
View File

@ -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;

2
net/core/dev.c
View File

@ -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);