ipv6: Check available headroom in ip6_xmit() even without options

[mirror_ubuntu-bionic-kernel.git] / net / ipv6 / ip6_output.c

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 9ab1e0fcbc13cec92c59feafedf947564437969c..7ca8264cbdf945f7b8a850c9d1140bb501c77316 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -195,37 +195,37 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
        const struct ipv6_pinfo *np = inet6_sk(sk);
        struct in6_addr *first_hop = &fl6->daddr;
        struct dst_entry *dst = skb_dst(skb);
+       unsigned int head_room;
        struct ipv6hdr *hdr;
        u8  proto = fl6->flowi6_proto;
        int seg_len = skb->len;
        int hlimit = -1;
        u32 mtu;
 
-       if (opt) {
-               unsigned int head_room;
+       head_room = sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dst->dev);
+       if (opt)
+               head_room += opt->opt_nflen + opt->opt_flen;
 
-               /* First: exthdrs may take lots of space (~8K for now)
-                  MAX_HEADER is not enough.
-                */
-               head_room = opt->opt_nflen + opt->opt_flen;
-               seg_len += head_room;
-               head_room += sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dst->dev);
-
-               if (skb_headroom(skb) < head_room) {
-                       struct sk_buff *skb2 = skb_realloc_headroom(skb, head_room);
-                       if (!skb2) {
-                               IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
-                                             IPSTATS_MIB_OUTDISCARDS);
-                               kfree_skb(skb);
-                               return -ENOBUFS;
-                       }
-                       if (skb->sk)
-                               skb_set_owner_w(skb2, skb->sk);
-                       consume_skb(skb);
-                       skb = skb2;
+       if (unlikely(skb_headroom(skb) < head_room)) {
+               struct sk_buff *skb2 = skb_realloc_headroom(skb, head_room);
+               if (!skb2) {
+                       IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
+                                     IPSTATS_MIB_OUTDISCARDS);
+                       kfree_skb(skb);
+                       return -ENOBUFS;
                }
+               if (skb->sk)
+                       skb_set_owner_w(skb2, skb->sk);
+               consume_skb(skb);
+               skb = skb2;
+       }
+
+       if (opt) {
+               seg_len += opt->opt_nflen + opt->opt_flen;
+
                if (opt->opt_flen)
                        ipv6_push_frag_opts(skb, opt, &proto);
+
                if (opt->opt_nflen)
                        ipv6_push_nfrag_opts(skb, opt, &proto, &first_hop,
                                             &fl6->saddr);