+/* Convert the IPv4 socket address IN into the equivalent IPv4-mapped IPv6
+ * address OUT.
+ */
+static void map_v4(struct socket *out, const struct socket *in)
+{
+ unsigned i;
+ in_addr_t a4 = ntohl(in->addr.ipv4.s_addr);
+
+ for (i = 0; i < 10; i++) out->addr.ipv6.s6_addr[i] = 0;
+ for (i = 10; i < 12; i++) out->addr.ipv6.s6_addr[i] = 0xff;
+ for (i = 0; i < 4; i++) out->addr.ipv6.s6_addr[15 - i] = (a4 >> 8*i)&0xff;
+ out->port = in->port;
+}
+
+/* Convert the IPv4-mapped IPv6 socket address IN into the equivalent IPv4
+ * address OUT; return -1 if the IN address isn't actually IPv4-mapped.
+ */
+static int unmap_v4(struct socket *out, const struct socket *in)
+{
+ unsigned i;
+ in_addr_t a4 = 0;
+
+ for (i = 0; i < 10; i++) if (in->addr.ipv6.s6_addr[i] != 0) return (-1);
+ for (i = 10; i < 12; i++) if (in->addr.ipv6.s6_addr[i] != 0xff) return (-1);
+ for (i = 0; i < 4; i++) a4 |= in->addr.ipv6.s6_addr[15 - i] << 8*i;
+ out->addr.ipv4.s_addr = htonl(a4);
+ out->port = in->port;
+ return (0);
+}
+