Fix #13: Check if IP address changed since last run, update A records

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

libmdnsd/mdnsd.c

@@ -77,6 +77,7 @@ struct cached {
 struct mdns_record {
  struct mdns_answer rr;
  char unique; /* # of checks performed to ensure */
+ int modified; /* Ignore conflicts after update at runtime */
  int tries;
  void (*conflict)(char *, int, void *);
  void *arg;
@@ -262,6 +263,8 @@ static void _r_push(mdns_record_t **list, mdns_record_t *r)
 /* Force any r out right away, if valid */
 static void _r_publish(mdns_daemon_t *d, mdns_record_t *r)
 {
+ r->modified = 1;
+
  if (r->unique && r->unique < 5)
  return; /* Probing already */
 
@@ -373,7 +376,8 @@ static void _r_done(mdns_daemon_t *d, mdns_record_t *r)
  if (d->published[i] == r)
  d->published[i] = r->next;
  else {
- for (cur = d->published[i]; cur && cur->next != r; cur = cur->next) ;
+ for (cur = d->published[i]; cur && cur->next != r; cur = cur->next)
+ ;
  if (cur)
  cur->next = r->next;
  }
@@ -570,6 +574,7 @@ static int _r_out(mdns_daemon_t *d, struct message *m, mdns_record_t **list)
 
  _a_copy(m, &r->rr);
 
+ r->modified = 0; /* If updated we've now sent the update. */
  if (r->rr.ttl == 0) {
  /*
  * also remove from other lists, because record
@@ -603,6 +608,30 @@ mdns_daemon_t *mdnsd_new(int class, int frame)
 
 void mdnsd_set_address(mdns_daemon_t *d, struct in_addr addr)
 {
+ int i;
+
+ if (!memcmp(&d->addr, &addr, sizeof(d->addr)))
+ return; /* No change */
+
+ for (i = 0; i < SPRIME; i++) {
+ mdns_record_t *r, *next;
+
+ r = d->published[i];
+ while (r != 0) {
+ next = r->next;
+
+ if (r->rr.type == QTYPE_A) {
+ mdnsd_set_raw(d, r, (char *)&addr, 4);
+// mdnsd_set_ip(d, r, mdnsd_get_address(d));
+
+ /* Republish, IP changed */
+ _r_push(&d->a_pause, r);
+ }
+
+ r = next;
+ }
+ }
+
  d->addr = addr;
 }
 
@@ -744,7 +773,7 @@ int mdnsd_in(mdns_daemon_t *d, struct message *m, unsigned long int ip, unsigned
  r_next = _r_next(d, r, m->qd[i].name, m->qd[i].type);
 
  /* probing state, check for conflicts */
- if (r->unique && r->unique < 5) {
+ if (r->unique && r->unique < 5 && !r->modified) {
  /* Check all to-be answers against our own */
  for (j = 0; j < m->nscount; j++) {
  if (m->qd[i].type != m->an[j].type || strcmp(m->qd[i].name, m->an[j].name))
@@ -797,8 +826,8 @@ int mdnsd_in(mdns_daemon_t *d, struct message *m, unsigned long int ip, unsigned
  }
 
  INFO("Got Answer: Name: %s, Type: %d", m->an[i].name, m->an[i].type);
- if ((r = _r_next(d, 0, m->an[i].name, m->an[i].type)) != 0 &&
-  r->unique && _a_match(&m->an[i], &r->rr) == 0)
+ r = _r_next(d, 0, m->an[i].name, m->an[i].type);
+ if (r != 0 && r->unique && !r->modified && _a_match(&m->an[i], &r->rr) == 0)
  _conflict(d, r);
 
  if (d->received_callback)

src/mdnsd.c

@@ -194,6 +194,7 @@ int main(int argc, char *argv[])
  char *path;
  char address[20];
  int persistent = 0;
+ int autoip = 1;
  int ttl = 255;
  int c, sd, rc;
 
@@ -202,6 +203,7 @@ int main(int argc, char *argv[])
  switch (c) {
  case 'a':
  inet_aton(optarg, &ina);
+ autoip = 0;
  break;
 
  case 'h':
@@ -255,12 +257,6 @@ int main(int argc, char *argv[])
  }
  }
 
- if (!ina.s_addr) {
- if (!getaddr(iface, address, sizeof(address)))
- errx(1, "Cannot find default interface, use -a ADDRESS");
- inet_aton(address, &ina);
- }
-
  d = mdnsd_new(QCLASS_IN, 1000);
  if (!d) {
  ERR("Failed creating daemon context: %s", strerror(errno));
@@ -294,6 +290,14 @@ int main(int argc, char *argv[])
  }
  }
 
+ /* Check if IP address changed, needed to update A records */
+ if (autoip && iface) {
+ if (!getaddr(iface, address, sizeof(address)))
+ errx(1, "Cannot find default interface, use -a ADDRESS");
+ inet_aton(address, &ina);
+ mdnsd_set_address(d, ina);
+ }
+
  rc = mdnsd_step(d, sd, FD_ISSET(sd, &fds), true, &tv);
  if (rc == 1) {
  ERR("Failed reading from socket %d: %s", errno, strerror(errno));