SADB_X_EXT_KMADDRESS
kma = ext_hdrs[SADB_X_EXT_KMADDRESS - 1];
kma->sadb_x_kmaddress_exttype = SADB_X_EXT_KMADDRESS;
[SADB_X_EXT_KMADDRESS] = (u8) sizeof(struct sadb_x_kmaddress),