Merge branch 'ipv6_ndisc'

YOSHIFUJI Hideaki says:

====================
This series of changes basically clean up NDISC logic,
especially on sender side.

We originally do For NS/NA/RS:
 1) build temporary ICMPv6 header
 2) ndisc_build_skb() with temporary ICMPv6 header and rather
    criptic arguments.
    - Calculate total length and allocate sk_buff
    - Build IPv6 header.
    - copy ICMPv6 header, additional data and ND options.
    - Fill-in ICMPv6 checksum.
    Here, structures defined for message format was not used
    at all, it is difficult to understand what is being sent,
    and it was not generic.
 3) __ndisc_send()
    - Allocate temporary dst.
    - Send it.

Several issues:
- We could not defer decision if we should/can send some ND
  option.
- It is hard to see the packet format at a glance.
- ICMPv6 header was built as temporary variable, and then
  copied to the buffer.
- Some code path for Redirect was not shared.

With these patches, we do:
 1) Calculate (or estimate) message length and option length.
 2) Allocate skb (via new ndisc_skb_alloc()).
 3) Fill-in ICMPv6 message directly using compound literals.
 4) Fill-in ICMPv6 checksum
 5) Build IPv6 header (including length)
 6) Send the packet (via ndisc_send_skb()).
    - allocate temporary dst and send it.

- We can defer calculating real length of the packet.
  For example, we can give up filling some option at when
  filling in.
- Message is built directly without temporary buffer.
- Structures defined for message format is easier to understand
  what is being built.
- NS/NA/RS/Redirect share same logic.
- Reduced code/data size:
	   text	   data	    bss	    dec	    hex	filename
	 265407	  14133	   3488	 283028	  45194	old/net/ipv6/ipv6.o
	 264955	  14109	   3488	 282552	  44fb8	new/net/ipv6/ipv6.o
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -661,13 +661,6 @@ extern int			ip6_xmit(struct sock *sk,
 					 struct ipv6_txoptions *opt,
 					 int tclass);
 
-extern int			ip6_nd_hdr(struct sock *sk,
-					   struct sk_buff *skb,
-					   struct net_device *dev,
-					   const struct in6_addr *saddr,
-					   const struct in6_addr *daddr,
-					   int proto, int len);
-
 extern int			ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr);
 
 extern int			ip6_append_data(struct sock *sk,

include/net/ndisc.h

@@ -127,13 +127,19 @@ static int ndisc_addr_option_pad(unsigned short type)
 	}
 }
 
+static inline int ndisc_opt_addr_space(struct net_device *dev)
+{
+	return NDISC_OPT_SPACE(dev->addr_len +
+			       ndisc_addr_option_pad(dev->type));
+}
+
 static inline u8 *ndisc_opt_addr_data(struct nd_opt_hdr *p,
 				      struct net_device *dev)
 {
 	u8 *lladdr = (u8 *)(p + 1);
 	int lladdrlen = p->nd_opt_len << 3;
 	int prepad = ndisc_addr_option_pad(dev->type);
-	if (lladdrlen != NDISC_OPT_SPACE(dev->addr_len + prepad))
+	if (lladdrlen != ndisc_opt_addr_space(dev))
 		return NULL;
 	return lladdr + prepad;
 }

net/ipv6/ip6_output.c

@@ -254,39 +254,6 @@ int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 
 EXPORT_SYMBOL(ip6_xmit);
 
-/*
- *	To avoid extra problems ND packets are send through this
- *	routine. It's code duplication but I really want to avoid
- *	extra checks since ipv6_build_header is used by TCP (which
- *	is for us performance critical)
- */
-
-int ip6_nd_hdr(struct sock *sk, struct sk_buff *skb, struct net_device *dev,
-	       const struct in6_addr *saddr, const struct in6_addr *daddr,
-	       int proto, int len)
-{
-	struct ipv6_pinfo *np = inet6_sk(sk);
-	struct ipv6hdr *hdr;
-
-	skb->protocol = htons(ETH_P_IPV6);
-	skb->dev = dev;
-
-	skb_reset_network_header(skb);
-	skb_put(skb, sizeof(struct ipv6hdr));
-	hdr = ipv6_hdr(skb);
-
-	ip6_flow_hdr(hdr, 0, 0);
-
-	hdr->payload_len = htons(len);
-	hdr->nexthdr = proto;
-	hdr->hop_limit = np->hop_limit;
-
-	hdr->saddr = *saddr;
-	hdr->daddr = *daddr;
-
-	return 0;
-}
-
 static int ip6_call_ra_chain(struct sk_buff *skb, int sel)
 {
 	struct ip6_ra_chain *ra;

net/ipv6/mcast.c

@@ -1313,6 +1313,31 @@ mld_scount(struct ifmcaddr6 *pmc, int type, int gdeleted, int sdeleted)
 	return scount;
 }
 
+static void ip6_mc_hdr(struct sock *sk, struct sk_buff *skb,
+		       struct net_device *dev,
+		       const struct in6_addr *saddr,
+		       const struct in6_addr *daddr,
+		       int proto, int len)
+{
+	struct ipv6hdr *hdr;
+
+	skb->protocol = htons(ETH_P_IPV6);
+	skb->dev = dev;
+
+	skb_reset_network_header(skb);
+	skb_put(skb, sizeof(struct ipv6hdr));
+	hdr = ipv6_hdr(skb);
+
+	ip6_flow_hdr(hdr, 0, 0);
+
+	hdr->payload_len = htons(len);
+	hdr->nexthdr = proto;
+	hdr->hop_limit = inet6_sk(sk)->hop_limit;
+
+	hdr->saddr = *saddr;
+	hdr->daddr = *daddr;
+}
+
 static struct sk_buff *mld_newpack(struct net_device *dev, int size)
 {
 	struct net *net = dev_net(dev);
@@ -1348,7 +1373,7 @@ static struct sk_buff *mld_newpack(struct net_device *dev, int size)
 	} else
 		saddr = &addr_buf;
 
-	ip6_nd_hdr(sk, skb, dev, saddr, &mld2_all_mcr, NEXTHDR_HOP, 0);
+	ip6_mc_hdr(sk, skb, dev, saddr, &mld2_all_mcr, NEXTHDR_HOP, 0);
 
 	memcpy(skb_put(skb, sizeof(ra)), ra, sizeof(ra));
 
@@ -1740,7 +1765,7 @@ static void igmp6_send(struct in6_addr *addr, struct net_device *dev, int type)
 	} else
 		saddr = &addr_buf;
 
-	ip6_nd_hdr(sk, skb, dev, saddr, snd_addr, NEXTHDR_HOP, payload_len);
+	ip6_mc_hdr(sk, skb, dev, saddr, snd_addr, NEXTHDR_HOP, payload_len);
 
 	memcpy(skb_put(skb, sizeof(ra)), ra, sizeof(ra));