Cc: Herbert Xu <herb...@gondor.apana.org.au>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
net/core/dev.c | 1 +
net/core/skbuff.c | 18 +++++++++++++++++-
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 368dc3b49dc0..ee0a4ac0bbb6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5787,6 +5787,7 @@ __sum16 __skb_gro_checksum_complete(struct sk_buff *skb)
/* NAPI_GRO_CB(skb)->csum holds pseudo checksum */
sum = csum_fold(csum_add(NAPI_GRO_CB(skb)->csum, wsum));
+ /* See comments in __skb_checksum_complete(). */
if (likely(!sum)) {
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
!skb->csum_complete_sw)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 6f2ea0f0fb75..530097df328f 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2637,6 +2637,7 @@ __sum16 __skb_checksum_complete_head(struct sk_buff *skb,
int len)
__sum16 sum;
sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
+ /* See comments in __skb_checksum_complete(). */
if (likely(!sum)) {
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
!skb->csum_complete_sw)
@@ -2648,6 +2649,15 @@ __sum16 __skb_checksum_complete_head(struct sk_buff
*skb, int len)
}
EXPORT_SYMBOL(__skb_checksum_complete_head);
+/* This function assumes skb->csum already holds pseudo header's checksum,
+ * which has been changed from the hardware checksum, for example, by
+ * __skb_checksum_validate_complete(). And, the original skb->csum must
+ * have been validated unsuccessfully for CHECKSUM_COMPLETE case.
+ *
+ * It returns non-zero if the recomputed checksum is still invalid, otherwise
+ * zero. The new checksum is stored back into skb->csum unless the skb is
+ * shared.
+ */
__sum16 __skb_checksum_complete(struct sk_buff *skb)
{
__wsum csum;
@@ -2655,8 +2665,14 @@ __sum16 __skb_checksum_complete(struct sk_buff *skb)
csum = skb_checksum(skb, 0, skb->len, 0);
- /* skb->csum holds pseudo checksum */
sum = csum_fold(csum_add(skb->csum, csum));
+ /* This check is inverted, because we already knew the hardware
+ * checksum is invalid before calling this function. So, if the
+ * re-computed checksum is valid instead, then we have a mismatch
+ * between the original skb->csum and skb_checksum(). This means either
+ * the original hardware checksum is incorrect or we screw up skb->csum
+ * when moving skb->data around.
+ */
if (likely(!sum)) {
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
!skb->csum_complete_sw)
--
2.19.1
