+
+static inline unsigned int ipv6_advmss(unsigned int mtu)
+{
+ mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
+
+ if (mtu < ip6_rt_min_advmss)
+ mtu = ip6_rt_min_advmss;
+
+ /*
+ * Maximal non-jumbo IPv6 payload is IPV6_MAXPLEN and
+ * corresponding MSS is IPV6_MAXPLEN - tcp_header_size.
+ * IPV6_MAXPLEN is also valid and means: "any MSS,
+ * rely only on pmtu discovery"
+ */
+ if (mtu > IPV6_MAXPLEN - sizeof(struct tcphdr))
+ mtu = IPV6_MAXPLEN;
+ return mtu;
+}