+static u_int32_t tcpmss_reverse_mtu(const struct sk_buff *skb,
+ unsigned int family)
+{
+ struct flowi fl = {};
+ const struct nf_afinfo *ai;
+ struct rtable *rt = NULL;
+ u_int32_t mtu = ~0U;
+
+ if (family == PF_INET)
+ fl.fl4_dst = ip_hdr(skb)->saddr;
+ else
+ fl.fl6_dst = ipv6_hdr(skb)->saddr;
+
+ rcu_read_lock();
+ ai = nf_get_afinfo(family);
+ if (ai != NULL)
+ ai->route((struct dst_entry **)&rt, &fl);
+ rcu_read_unlock();
+
+ if (rt != NULL) {
+ mtu = dst_mtu(&rt->u.dst);
+ dst_release(&rt->u.dst);
+ }
+ return mtu;
+}
+