1 files changed, 69 insertions, 2 deletions

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index e9f1217a8afd..f3869c186d97 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -39,6 +39,71 @@
 #include <net/route.h>
 #include <net/xfrm.h>
 
+static bool ip_may_fragment(const struct sk_buff *skb)
+{
+        return unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0) ||
+               !skb->local_df;
+}
+
+static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
+{
+        if (skb->len <= mtu || skb->local_df)
+                return false;
+
+        if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
+                return false;
+
+        return true;
+}
+
+static bool ip_gso_exceeds_dst_mtu(const struct sk_buff *skb)
+{
+        unsigned int mtu;
+
+        if (skb->local_df || !skb_is_gso(skb))
+                return false;
+
+        mtu = ip_dst_mtu_maybe_forward(skb_dst(skb), true);
+
+        /* if seglen > mtu, do software segmentation for IP fragmentation on
+         * output.  DF bit cannot be set since ip_forward would have sent
+         * icmp error.
+         */
+        return skb_gso_network_seglen(skb) > mtu;
+}
+
+/* called if GSO skb needs to be fragmented on forward */
+static int ip_forward_finish_gso(struct sk_buff *skb)
+{
+        struct dst_entry *dst = skb_dst(skb);
+        netdev_features_t features;
+        struct sk_buff *segs;
+        int ret = 0;
+
+        features = netif_skb_dev_features(skb, dst->dev);
+        segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
+        if (IS_ERR(segs)) {
+                kfree_skb(skb);
+                return -ENOMEM;
+        }
+
+        consume_skb(skb);
+
+        do {
+                struct sk_buff *nskb = segs->next;
+                int err;
+
+                segs->next = NULL;
+                err = dst_output(segs);
+
+                if (err && ret == 0)
+                        ret = err;
+                segs = nskb;
+        } while (segs);
+
+        return ret;
+}
+
 static int ip_forward_finish(struct sk_buff *skb)
 {
         struct ip_options *opt  = &(IPCB(skb)->opt);
@@ -49,6 +114,9 @@ static int ip_forward_finish(struct sk_buff *skb)
         if (unlikely(opt->optlen))
                 ip_forward_options(skb);
 
+        if (ip_gso_exceeds_dst_mtu(skb))
+                return ip_forward_finish_gso(skb);
+
         return dst_output(skb);
 }
 
@@ -91,8 +159,7 @@ int ip_forward(struct sk_buff *skb)
 
         IPCB(skb)->flags |= IPSKB_FORWARDED;
         mtu = ip_dst_mtu_maybe_forward(&rt->dst, true);
-        if (unlikely(skb->len > mtu && !skb_is_gso(skb) &&
-                     (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
+        if (!ip_may_fragment(skb) && ip_exceeds_mtu(skb, mtu)) {
                 IP_INC_STATS(dev_net(rt->dst.dev), IPSTATS_MIB_FRAGFAILS);
                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
                           htonl(mtu));