Fix locking/race for tdns error logging

Patch by: michaelortmann

Author: michaelortmann

src/dns.c

@@ -504,6 +504,7 @@ void *thread_dns_hostbyip(void *arg)
 
   i = getnameinfo((const struct sockaddr *) &addr->addr.sa, addr->addrlen,
                   dtn->host, sizeof dtn->host, NULL, 0, 0);
+  pthread_mutex_lock(&dtn->mutex);
   if (!i)
     *dtn->strerror = 0;
   else {
@@ -515,7 +516,6 @@ void *thread_dns_hostbyip(void *arg)
 #endif
       inet_ntop(AF_INET, &addr->addr.s4.sin_addr.s_addr, dtn->host, sizeof dtn->host);
   }
-  pthread_mutex_lock(&dtn->mutex);
   close(dtn->fildes[1]);
   pthread_mutex_unlock(&dtn->mutex);
   return NULL;
@@ -530,6 +530,7 @@ void *thread_dns_ipbyhost(void *arg)
 
   error = getaddrinfo(dtn->host, NULL, NULL, &res0);
   memset(addr, 0, sizeof *addr);
+  pthread_mutex_lock(&dtn->mutex);
   if (!error) {
     *dtn->strerror = 0;
 #ifdef IPV6
@@ -563,11 +564,13 @@ void *thread_dns_ipbyhost(void *arg)
   }
   else if (error == EAI_NONAME)
     snprintf(dtn->strerror, sizeof dtn->strerror, "dns: thread_dns_ipbyhost(): getaddrinfo(): not known");
-  else if (error == EAI_SYSTEM)
-    snprintf(dtn->strerror, sizeof dtn->strerror, "dns: thread_dns_ipbyhost(): getaddrinfo(): %s: %s", gai_strerror(error), strerror(errno));
-  else
+  else if (error == EAI_SYSTEM) {
+    char ebuf[2048];
+    if (strerror_r(errno, ebuf, sizeof ebuf))
+      strcpy(ebuf, "strerror_r()");
+    snprintf(dtn->strerror, sizeof dtn->strerror, "dns: thread_dns_ipbyhost(): getaddrinfo(): %s: %s", gai_strerror(error), ebuf);
+  } else
     snprintf(dtn->strerror, sizeof dtn->strerror, "dns: thread_dns_ipbyhost(): getaddrinfo(): %s", gai_strerror(error));
-  pthread_mutex_lock(&dtn->mutex);
   close(dtn->fildes[1]);
   pthread_mutex_unlock(&dtn->mutex);
   return NULL;

src/net.c

@@ -1061,27 +1061,24 @@ int sockread(char *s, int *len, sock_list *slist, int slistmax, int tclonly)
 #ifdef EGG_TDNS
   dtn_prev = dns_thread_head;
   for (dtn = dtn_prev->next; dtn; dtn = dtn->next) {
+    pthread_mutex_lock(&dtn->mutex);
     if (*dtn->strerror)
       debug2("%s: hostname %s", dtn->strerror, dtn->host);
     fd = dtn->fildes[0];
     if (FD_ISSET(fd, &fdr)) {
-      if (dtn->type == DTN_TYPE_HOSTBYIP) {
-        pthread_mutex_lock(&dtn->mutex);
+      if (dtn->type == DTN_TYPE_HOSTBYIP)
         call_hostbyip(&dtn->addr, dtn->host, !*dtn->strerror);
-        pthread_mutex_unlock(&dtn->mutex);
-      }
-      else {
-        pthread_mutex_lock(&dtn->mutex);
+      else
         call_ipbyhost(dtn->host, &dtn->addr, !*dtn->strerror);
-        pthread_mutex_unlock(&dtn->mutex);
-      }
-      close(dtn->fildes[0]);
+      pthread_mutex_unlock(&dtn->mutex);
+      close(fd);
       if (pthread_join(dtn->thread_id, &res))
         putlog(LOG_MISC, "*", "sockread(): pthread_join(): error = %s", strerror(errno));
       dtn_prev->next = dtn->next;
       nfree(dtn);
       dtn = dtn_prev;
-    }
+    } else
+      pthread_mutex_unlock(&dtn->mutex);
     dtn_prev = dtn;
   }
 #endif