diff options
Diffstat (limited to 'config.c')
| -rw-r--r-- | config.c | 70 |
1 files changed, 68 insertions, 2 deletions
@@ -185,7 +185,12 @@ void dns64_detection(unsigned net_id) { } } - +/* function: gen_random_iid + * picks a random interface ID that is checksum neutral with the IPv4 address and the NAT64 prefix + * myaddr - IPv6 address to write to + * ipv4_local_subnet - clat IPv4 address + * plat_subnet - NAT64 prefix + */ void gen_random_iid(struct in6_addr *myaddr, struct in_addr *ipv4_local_subnet, struct in6_addr *plat_subnet) { // Fill last 8 bytes of IPv6 address with random bits. @@ -208,6 +213,61 @@ void gen_random_iid(struct in6_addr *myaddr, struct in_addr *ipv4_local_subnet, myaddr->s6_addr[12] = delta & 0xff; } +// Factored out to a separate function for testability. +int connect_is_ipv4_address_free(in_addr_t addr) { + int s = socket(AF_INET, SOCK_DGRAM, 0); + if (s == -1) { + return 0; + } + + // Attempt to connect to the address. If the connection succeeds and getsockname returns the same + // the address then the address is already assigned to the system and we can't use it. + struct sockaddr_in sin = { .sin_family = AF_INET, .sin_addr = { addr }, .sin_port = 53 }; + socklen_t len = sizeof(sin); + int inuse = connect(s, (struct sockaddr *) &sin, sizeof(sin)) == 0 && + getsockname(s, (struct sockaddr *) &sin, &len) == 0 && + (size_t) len >= sizeof(sin) && + sin.sin_addr.s_addr == addr; + + close(s); + return !inuse; +} + +addr_free_func config_is_ipv4_address_free = connect_is_ipv4_address_free; + +/* function: config_select_ipv4_address + * picks a free IPv4 address, starting from ip and trying all addresses in the prefix in order + * ip - the IP address from the configuration file + * prefixlen - the length of the prefix from which addresses may be selected. + * returns: the IPv4 address, or INADDR_NONE if no addresses were available + */ +in_addr_t config_select_ipv4_address(const struct in_addr *ip, int16_t prefixlen) { + in_addr_t chosen = INADDR_NONE; + + // Don't accept prefixes that are too large because we scan addresses one by one. + if (prefixlen < 16 || prefixlen > 32) { + return chosen; + } + + // All these are in host byte order. + in_addr_t mask = 0xffffffff >> (32 - prefixlen) << (32 - prefixlen); + in_addr_t ipv4 = ntohl(ip->s_addr); + in_addr_t first_ipv4 = ipv4; + in_addr_t prefix = ipv4 & mask; + + // Pick the first IPv4 address in the pool, wrapping around if necessary. + // So, for example, 192.0.0.4 -> 192.0.0.5 -> 192.0.0.6 -> 192.0.0.7 -> 192.0.0.0. + do { + if (config_is_ipv4_address_free(htonl(ipv4))) { + chosen = htonl(ipv4); + break; + } + ipv4 = prefix | ((ipv4 + 1) & ~mask); + } while (ipv4 != first_ipv4); + + return chosen; +} + /* function: config_generate_local_ipv6_subnet * generates the local ipv6 subnet when given the interface ip * requires config.ipv6_host_id @@ -264,7 +324,12 @@ int read_config(const char *file, const char *uplink_interface, const char *plat if(!config_item_int16_t(root, "ipv4mtu", "-1", &Global_Clatd_Config.ipv4mtu)) goto failed; - if(!config_item_ip(root, "ipv4_local_subnet", DEFAULT_IPV4_LOCAL_SUBNET, &Global_Clatd_Config.ipv4_local_subnet)) + if(!config_item_ip(root, "ipv4_local_subnet", DEFAULT_IPV4_LOCAL_SUBNET, + &Global_Clatd_Config.ipv4_local_subnet)) + goto failed; + + if(!config_item_int16_t(root, "ipv4_local_prefixlen", DEFAULT_IPV4_LOCAL_PREFIXLEN, + &Global_Clatd_Config.ipv4_local_prefixlen)) goto failed; if(plat_prefix) { // plat subnet is coming from the command line @@ -311,6 +376,7 @@ void dump_config() { logmsg(ANDROID_LOG_DEBUG,"ipv4mtu = %d",Global_Clatd_Config.ipv4mtu); logmsg(ANDROID_LOG_DEBUG,"ipv6_local_subnet = %s",inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, charbuffer, sizeof(charbuffer))); logmsg(ANDROID_LOG_DEBUG,"ipv4_local_subnet = %s",inet_ntop(AF_INET, &Global_Clatd_Config.ipv4_local_subnet, charbuffer, sizeof(charbuffer))); + logmsg(ANDROID_LOG_DEBUG,"ipv4_local_prefixlen = %d", Global_Clatd_Config.ipv4_local_prefixlen); logmsg(ANDROID_LOG_DEBUG,"plat_subnet = %s",inet_ntop(AF_INET6, &Global_Clatd_Config.plat_subnet, charbuffer, sizeof(charbuffer))); logmsg(ANDROID_LOG_DEBUG,"default_pdp_interface = %s",Global_Clatd_Config.default_pdp_interface); } |