// Returns AF_MAX (with errno set) if error, AF_UNSPEC if no more addrs (socket closed)
struct IPAddr nextAddr(struct AddrFilter const filter, struct MonitorState * const state){
// NLMSG_OK checks length first, so safe to call with state->nlh == NULL iff
// state->nlmsg_len < (int) sizeof(struct nlmsghdr)
if (NLMSG_OK(state->nlh, state->nlmsg_len) && (state->nlh->nlmsg_type != NLMSG_DONE)){
struct nlmsghdr * nlh = state->nlh;
state->nlh = NLMSG_NEXT(state->nlh, state->nlmsg_len);
switch(nlh->nlmsg_type){
case NLMSG_ERROR:
errno = -((struct nlmsgerr *) NLMSG_DATA(nlh))->error;
struct IPAddr addr = {.af = AF_MAX};
return addr;
case RTM_NEWADDR: {
struct ifaddrmsg * ifa = (struct ifaddrmsg *) NLMSG_DATA(nlh);
if (!filterIfAddrMsg(*ifa, filter))
return nextAddr(filter, state);
{
struct rtattr * rth;
size_t rtmsg_len;
for (rth = IFA_RTA(ifa), rtmsg_len = IFA_PAYLOAD(nlh);
RTA_OK(rth, rtmsg_len); RTA_NEXT(rth, rtmsg_len)){
if (rth->rta_type != IFA_ADDRESS)
continue;
// family checked in filterIfAddrMsg, so always valid.
struct IPAddr addr = {.af = ifa->ifa_family};
switch (ifa->ifa_family) {
case AF_INET:
addr.ipv4 = *((struct in_addr *) RTA_DATA(rth));
break;
case AF_INET6:
addr.ipv6 = *((struct in6_addr *) RTA_DATA(rth));
break;
}
if (addrIsPrivate(addr) && !filter.allow_private)
return nextAddr(filter, state);
else
return addr;
}
}
// Recieved RTM_NEWADDR without any address.
errno = EBADMSG;
struct IPAddr addr = {.af = AF_MAX};
return addr;
}
default:
return nextAddr(filter, state);
}
} else {
state->nlmsg_len = nextMessage(filter, state->socket, &state->buf, &state->buf_len);
if (state->nlmsg_len == 0) {
// Socket closed by kernel
struct IPAddr addr = {.af = AF_UNSPEC};
return addr;
} else if (state->nlmsg_len < 0) {
// Socket error
struct IPAddr addr = {.af = AF_MAX};
return addr;
} else {
int main(int const argc, char** argv) {
struct AddrFilter filter = {.allow_private = false};
int (* addr_processor)(struct IPAddr);
// Deal with options
const char short_opts[] = "vVh46pa";
struct option long_opts[] = {
{"allow-private", no_argument, 0, 'p'},
{"process-all", no_argument, 0, 'a'},
{"verbose", no_argument, 0, 'v'},
{"version", no_argument, 0, 'V'},
{"help", no_argument, 0, 'h'},
};
bool verbosity = 0;
bool process_all = false;
int opt_index = 0;
char opt;
while ((opt = getopt_long(argc, argv, short_opts, long_opts, &opt_index)) != -1) {
switch (opt) {
case 'a':
process_all = true;
break;
case 'v':
verbosity = 1;
break;
case 'V':
puts(version);
return EXIT_SUCCESS;
case '4':
addFilterAf(&filter, AF_INET);
break;
case '6':
addFilterAf(&filter, AF_INET6);
break;
case 'p':
filter.allow_private = true;
break;
case 'h':
printUsage();
return EXIT_SUCCESS;
default:
printUsage();
return EXIT_USAGE;
}
}
// Listen for all changes if none specified.
if (filter.num_af == 0){
addFilterAf(&filter, AF_INET);
addFilterAf(&filter, AF_INET6);
}
switch ((argc - optind)){
case 1:
addr_processor = printAddr;
break;
case 2:
setUrl(argv[optind + 1]);
addr_processor = webUpdate;
break;
default:
puts("Usage:\n");
printUsage();
return EXIT_USAGE;
}
char const * const iface_name = argv[optind];
filter.iface = if_nametoindex(iface_name);
if (!filter.iface) {
fprintf(stderr, "Error resolving interface %s: %s\n",
iface_name, strerror(errno));
return EXIT_FAILURE;
}
if (verbosity){
puts("Running in verbose mode.");
printf("Listening on interfaces: %s (#%d)\n", iface_name, filter.iface);
fputs("Listening for address changes in:", stdout);
if (checkFilterAf(filter, AF_INET))
printf(" IPv4");
if (checkFilterAf(filter, AF_INET6))
printf(" IPv6");
puts("");
}
// Prepare monitoring, cleanup necessary if exiting after this point.
struct MonitorState state;
if (!initState(filter, &state, 1024)){
perror("Couldn't set up for monitoring");
return EXIT_FAILURE;
}
// Main loop
pid_t child = -1;
do {
struct IPAddr new_addr = nextAddr(filter, &state);
if (child != -1){
// Make sure kill isn't called on first loop.
if (!process_all)
kill(child, termsig);
int status;
if (waitpid(child, &status, 0) == -1){
perror("Error waiting for child");
break;
}
if (!childOK(status))
break;
}
if (new_addr.af == AF_MAX){
perror("An error occurred while waiting for a new IP");
break;
} else if (new_addr.af == AF_UNSPEC) {
fputs("Netlink socket closed by kernel.", stderr);
break;
}
// TODO: Could use exec
child = fork();
if (child == -1){
perror("Could not fork to process new address.");
break;
} else if (!child){
close(state.socket); // Make sure to set CLOEXEC if changing to exec.
return addr_processor(new_addr);
}
} while (true);
close(state.socket);
free(state.buf);
return EXIT_FAILURE;
}