net_sched: fix mirrored packets checksum

Similar to commit 9b368814 ("net: fix bridge multicast packet checksum validation")
we need to fixup the checksum for CHECKSUM_COMPLETE when
pushing skb on RX path. Otherwise we get similar splats.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Tom Herbert <tom@herbertland.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -2870,6 +2870,25 @@ static inline void skb_postpush_rcsum(struct sk_buff *skb,
 		skb->csum = csum_partial(start, len, skb->csum);
 }
 
+/**
+ *	skb_push_rcsum - push skb and update receive checksum
+ *	@skb: buffer to update
+ *	@len: length of data pulled
+ *
+ *	This function performs an skb_push on the packet and updates
+ *	the CHECKSUM_COMPLETE checksum.  It should be used on
+ *	receive path processing instead of skb_push unless you know
+ *	that the checksum difference is zero (e.g., a valid IP header)
+ *	or you are setting ip_summed to CHECKSUM_NONE.
+ */
+static inline unsigned char *skb_push_rcsum(struct sk_buff *skb,
+					    unsigned int len)
+{
+	skb_push(skb, len);
+	skb_postpush_rcsum(skb, skb->data, len);
+	return skb->data;
+}
+
 /**
  *	pskb_trim_rcsum - trim received skb and update checksum
  *	@skb: buffer to trim

net/core/skbuff.c

@@ -3015,24 +3015,6 @@ int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
 }
 EXPORT_SYMBOL_GPL(skb_append_pagefrags);
 
-/**
- *	skb_push_rcsum - push skb and update receive checksum
- *	@skb: buffer to update
- *	@len: length of data pulled
- *
- *	This function performs an skb_push on the packet and updates
- *	the CHECKSUM_COMPLETE checksum.  It should be used on
- *	receive path processing instead of skb_push unless you know
- *	that the checksum difference is zero (e.g., a valid IP header)
- *	or you are setting ip_summed to CHECKSUM_NONE.
- */
-static unsigned char *skb_push_rcsum(struct sk_buff *skb, unsigned len)
-{
-	skb_push(skb, len);
-	skb_postpush_rcsum(skb, skb->data, len);
-	return skb->data;
-}
-
 /**
  *	skb_pull_rcsum - pull skb and update receive checksum
  *	@skb: buffer to update

net/sched/act_mirred.c

@@ -181,7 +181,7 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
 
 	if (!(at & AT_EGRESS)) {
 		if (m->tcfm_ok_push)
-			skb_push(skb2, skb->mac_len);
+			skb_push_rcsum(skb2, skb->mac_len);
 	}
 
 	/* mirror is always swallowed */