[PATCH net-next,v3 5/9] net: ipv4: place control buffer handling away from fragmentation iterators

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

Deal with the IPCB() area away from the iterators.

The bridge codebase has its own control buffer layout, move specific
IP control buffer handling into the IPv4 codepath.

Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
 net/ipv4/ip_output.c | 55 +++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 37 insertions(+), 18 deletions(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index c3f139843eca..8bae773cafbd 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -525,9 +525,6 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 
 	skb_copy_hash(to, from);
 
-	/* Copy the flags to each fragment. */
-	IPCB(to)->flags = IPCB(from)->flags;
-
 #ifdef CONFIG_NET_SCHED
 	to->tc_index = from->tc_index;
 #endif
@@ -582,6 +579,18 @@ void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
 }
 EXPORT_SYMBOL(ip_fraglist_init);
 
+static void ip_fraglist_ipcb_prepare(struct sk_buff *skb,
+				     struct ip_fraglist_iter *iter)
+{
+	struct sk_buff *to = iter->frag;
+
+	/* Copy the flags to each fragment. */
+	IPCB(to)->flags = IPCB(skb)->flags;
+
+	if (iter->offset == 0)
+		ip_options_fragment(to);
+}
+
 void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
 {
 	unsigned int hlen = iter->hlen;
@@ -598,8 +607,6 @@ void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
 	iph = iter->iph;
 	iph->tot_len = htons(frag->len);
 	ip_copy_metadata(frag, skb);
-	if (iter->offset == 0)
-		ip_options_fragment(frag);
 	iter->offset += skb->len - hlen;
 	iph->frag_off = htons(iter->offset >> 3);
 	if (frag->next)
@@ -627,6 +634,25 @@ void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
 }
 EXPORT_SYMBOL(ip_frag_init);
 
+static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to,
+			 bool first_frag, struct ip_frag_state *state)
+{
+	/* Copy the flags to each fragment. */
+	IPCB(to)->flags = IPCB(from)->flags;
+
+	if (IPCB(from)->flags & IPSKB_FRAG_PMTU)
+		state->iph->frag_off |= htons(IP_DF);
+
+	/* ANK: dirty, but effective trick. Upgrade options only if
+	 * the segment to be fragmented was THE FIRST (otherwise,
+	 * options are already fixed) and make it ONCE
+	 * on the initial skb, so that all the following fragments
+	 * will inherit fixed options.
+	 */
+	if (first_frag)
+		ip_options_fragment(from);
+}
+
 struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
 {
 	unsigned int len = state->left;
@@ -685,18 +711,6 @@ struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
 	iph = ip_hdr(skb2);
 	iph->frag_off = htons((state->offset >> 3));
 
-	if (IPCB(skb)->flags & IPSKB_FRAG_PMTU)
-		iph->frag_off |= htons(IP_DF);
-
-	/* ANK: dirty, but effective trick. Upgrade options only if
-	 * the segment to be fragmented was THE FIRST (otherwise,
-	 * options are already fixed) and make it ONCE
-	 * on the initial skb, so that all the following fragments
-	 * will inherit fixed options.
-	 */
-	if (state->offset == 0)
-		ip_options_fragment(skb);
-
 	/*
 	 *	Added AC : If we are fragmenting a fragment that's not the
 	 *		   last fragment then keep MF on each bit
@@ -799,8 +813,10 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 		for (;;) {
 			/* Prepare header of the next frame,
 			 * before previous one went down. */
-			if (iter.frag)
+			if (iter.frag) {
+				ip_fraglist_ipcb_prepare(skb, &iter);
 				ip_fraglist_prepare(skb, &iter);
+			}
 
 			err = output(net, sk, skb);
 
@@ -844,11 +860,14 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 	 */
 
 	while (state.left > 0) {
+		bool first_frag = (state.offset == 0);
+
 		skb2 = ip_frag_next(skb, &state);
 		if (IS_ERR(skb2)) {
 			err = PTR_ERR(skb2);
 			goto fail;
 		}
+		ip_frag_ipcb(skb, skb2, first_frag, &state);
 
 		/*
 		 *	Put this fragment into the sending queue.
-- 
2.11.0