ipv4: introduce ip_dst_mtu_maybe_forward and protect forwarding path against pmtu...

[~andy/linux] / net / ipv4 / ip_output.c

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 912402752f2ffce701d697de1bb7a32b05c3b482..9a78804cfe9c457a94c3b4c5f2e7d8fe0eb604dd 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -449,6 +449,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
        __be16 not_last_frag;
        struct rtable *rt = skb_rtable(skb);
        int err = 0;
+       bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;
 
        dev = rt->dst.dev;
 
@@ -458,12 +459,13 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 
        iph = ip_hdr(skb);
 
+       mtu = ip_dst_mtu_maybe_forward(&rt->dst, forwarding);
        if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) ||
                     (IPCB(skb)->frag_max_size &&
-                     IPCB(skb)->frag_max_size > dst_mtu(&rt->dst)))) {
+                     IPCB(skb)->frag_max_size > mtu))) {
                IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
-                         htonl(ip_skb_dst_mtu(skb)));
+                         htonl(mtu));
                kfree_skb(skb);
                return -EMSGSIZE;
        }
@@ -473,7 +475,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
         */
 
        hlen = iph->ihl * 4;
-       mtu = dst_mtu(&rt->dst) - hlen; /* Size of data space */
+       mtu = mtu - hlen;       /* Size of data space */
 #ifdef CONFIG_BRIDGE_NETFILTER
        if (skb->nf_bridge)
                mtu -= nf_bridge_mtu_reduction(skb);
@@ -828,7 +830,7 @@ static int __ip_append_data(struct sock *sk,
 
        if (cork->length + length > maxnonfragsize - fragheaderlen) {
                ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
-                              mtu-exthdrlen);
+                              mtu - (opt ? opt->optlen : 0));
                return -EMSGSIZE;
        }
 
@@ -1151,7 +1153,8 @@ ssize_t   ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
                         mtu : 0xFFFF;
 
        if (cork->length + size > maxnonfragsize - fragheaderlen) {
-               ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport, mtu);
+               ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
+                              mtu - (opt ? opt->optlen : 0));
                return -EMSGSIZE;
        }