From: Ben Pfaff <blp@nicira.com>
Date: Tue, 11 Nov 2008 23:40:28 +0000 (-0800)
Subject: Fix datapath make_writable() function.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4a5396937e998ae8b9a281871e213545b2953f6c;p=openvswitch

Fix datapath make_writable() function.

- We weren't necessarily pulling enough into the headers in the non-shared
  case, since the IP header by itself can be longer than 40 bytes.

- The skb is guaranteed not to have a destructor at this point.
---

diff --git a/datapath/dp_act.c b/datapath/dp_act.c
index daa319a2..14eaac33 100644
--- a/datapath/dp_act.c
+++ b/datapath/dp_act.c
@@ -502,26 +502,17 @@ void execute_actions(struct datapath *dp, struct sk_buff *skb,
 int
 make_writable(struct sk_buff **pskb)
 {
-	/* Based on skb_make_writable() in net/netfilter/core.c. */
-	struct sk_buff *nskb;
-
-	/* Not exclusive use of packet?  Must copy. */
-	if (skb_shared(*pskb) || skb_cloned(*pskb))
-		goto copy_skb;
-
-	return pskb_may_pull(*pskb, 40); /* FIXME? */
-
-copy_skb:
-	nskb = skb_copy(*pskb, GFP_ATOMIC);
-	if (!nskb)
-		return 0;
-	BUG_ON(skb_is_nonlinear(nskb));
-
-	/* Rest of kernel will get very unhappy if we pass it a
-	   suddenly-orphaned skbuff */
-	if ((*pskb)->sk)
-		skb_set_owner_w(nskb, (*pskb)->sk);
-	kfree_skb(*pskb);
-	*pskb = nskb;
-	return 1;
+	struct sk_buff *skb = *pskb;
+	if (skb_shared(skb) || skb_cloned(skb)) {
+		struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
+		if (!nskb)
+			return 0;
+		kfree_skb(skb);
+		*pskb = nskb;
+		return 1;
+	} else {
+		unsigned int hdr_len = (skb_transport_offset(skb)
+					+ sizeof(struct tcphdr));
+		return pskb_may_pull(skb, min(hdr_len, skb->len));
+	}
 }