ndisc: Defer building IPv6 header.

Build ICMPv6 message first and make buffer management easier;
we can use skb->len when filling checksum in ICMPv6 header,
and then build IP header with length field.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 11 deletions

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 200b2b22b9ba..09171fdbc312 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -387,7 +387,7 @@ static struct sk_buff *ndisc_alloc_skb(struct net_device *dev,
         skb->protocol = htons(ETH_P_IPV6);
         skb->dev = dev;
 
-        skb_reserve(skb, hlen);
+        skb_reserve(skb, hlen + sizeof(struct ipv6hdr));
 
         return skb;
 }
@@ -399,8 +399,8 @@ static void ip6_nd_hdr(struct sk_buff *skb,
 {
         struct ipv6hdr *hdr;
 
+        skb_push(skb, sizeof(*hdr));
         skb_reset_network_header(skb);
-        skb_put(skb, sizeof(struct ipv6hdr));
         hdr = ipv6_hdr(skb);
 
         ip6_flow_hdr(hdr, 0, 0);
@@ -438,8 +438,6 @@ static struct sk_buff *ndisc_build_skb(struct net_device *dev,
         if (!skb)
                 return NULL;
 
-        ip6_nd_hdr(skb, saddr, daddr, inet6_sk(sk)->hop_limit, len);
-
         skb->transport_header = skb->tail;
         skb_put(skb, len);
 
@@ -455,10 +453,12 @@ static struct sk_buff *ndisc_build_skb(struct net_device *dev,
         if (llinfo)
                 ndisc_fill_addr_option(opt, llinfo, dev->dev_addr, dev);
 
-        hdr->icmp6_cksum = csum_ipv6_magic(saddr, daddr, len,
+        hdr->icmp6_cksum = csum_ipv6_magic(saddr, daddr, skb->len,
                                            IPPROTO_ICMPV6,
                                            csum_partial(hdr,
-                                                        len, 0));
+                                                        skb->len, 0));
+
+        ip6_nd_hdr(skb, saddr, daddr, inet6_sk(sk)->hop_limit, skb->len);
 
         return skb;
 }
@@ -1479,9 +1479,6 @@ void ndisc_send_redirect(struct sk_buff *skb, const struct in6_addr *target)
         if (!buff)
                 goto release;
 
-        ip6_nd_hdr(buff, &saddr_buf, &ipv6_hdr(skb)->saddr,
-                   inet6_sk(sk)->hop_limit, len);
-
         skb_set_transport_header(buff, skb_tail_pointer(buff) - buff->data);
         skb_put(buff, len);
         msg = (struct rd_msg *)icmp6_hdr(buff);
@@ -1513,8 +1510,11 @@ void ndisc_send_redirect(struct sk_buff *skb, const struct in6_addr *target)
                 opt = ndisc_fill_redirect_hdr_option(opt, skb, rd_len);
 
         msg->icmph.icmp6_cksum = csum_ipv6_magic(&saddr_buf, &ipv6_hdr(skb)->saddr,
-                                                 len, IPPROTO_ICMPV6,
-                                                 csum_partial(msg, len, 0));
+                                                 buff->len, IPPROTO_ICMPV6,
+                                                 csum_partial(msg, buff->len, 0));
+
+        ip6_nd_hdr(buff, &saddr_buf, &ipv6_hdr(skb)->saddr,
+                   inet6_sk(sk)->hop_limit, buff->len);
 
         skb_dst_set(buff, dst);
         rcu_read_lock();