Optimize comparison of similar sockets

Take advantage from de-duplication done in allocate_sfd. Create a new
special case, when sfd is created, but its fd is not. Such case is used
for interface bound sockets only with random outgoing ports.

Speed up searching in random sockets. Server members are not compared
one after one, but just pointer to sfd is compared. We ensure each
serverfd is unique, so different pointers means different servers.

Author: pemensik

src/dnsmasq.c

@@ -1691,7 +1691,8 @@ static int set_dns_listeners(time_t now)
     get_new_frec(now, &wait, NULL);
 
   for (serverfdp = daemon->sfds; serverfdp; serverfdp = serverfdp->next)
-    poll_listen(serverfdp->fd, POLLIN);
+    if (serverfdp->fd != -1)
+      poll_listen(serverfdp->fd, POLLIN);
 
   for (i = 0; i < RANDOM_SOCKS; i++)
     if (daemon->randomsocks[i].refcount != 0)
@@ -1742,7 +1743,7 @@ static void check_dns_listeners(time_t now)
   int pipefd[2];
 
   for (serverfdp = daemon->sfds; serverfdp; serverfdp = serverfdp->next)
-    if (poll_check(serverfdp->fd, POLLIN))
+    if (serverfdp->fd != -1 && poll_check(serverfdp->fd, POLLIN))
       reply_query(serverfdp->fd, now);
 
   for (i = 0; i < RANDOM_SOCKS; i++)

src/dnsmasq.h

@@ -541,16 +541,19 @@ union mysockaddr {
 #define SERV_GOT_TCP       32768  /* Got some data from the TCP connection */
 
 struct serverfd {
-  int fd;
+  int fd; /* -1 when random sockets are used */
   union mysockaddr source_addr;
   char interface[IF_NAMESIZE+1];
   unsigned int ifindex, used, preallocated;
   struct serverfd *next;
 };
 
+#define SERVERFD_INVALID ((struct serverfd *) ~0)
+
 struct randfd {
-  struct server *serv;
+  struct serverfd *sfd; /* might be set to SERVERFD_INVALID */
   int fd;
+  short family; /* needed when sfd == NULL */
   unsigned short refcount; /* refcount == 0xffff means overflow record. */
 };
 

src/forward.c

@@ -2174,16 +2174,6 @@ static int random_sock(struct server *s)
   return -1;
 }
 
-/* compare source addresses and interface, serv2 can be null. */
-static int server_isequal(const struct server *serv1,
-			 const struct server *serv2)
-{
-  return (serv2 &&
-    serv2->ifindex == serv1->ifindex &&
-    sockaddr_isequal(&serv2->source_addr, &serv1->source_addr) &&
-    strncmp(serv2->interface, serv1->interface, IF_NAMESIZE) == 0);
-}
-
 /* fdlp points to chain of randomfds already in use by transaction.
    If there's already a suitable one, return it, else allocate a 
    new one and add it to the list. 
@@ -2202,12 +2192,13 @@ int allocate_rfd(struct randfd_list **fdlp, struct server *serv)
   int fd = 0;
 
   /* If server has a pre-allocated fd, use that. */
-  if (serv->sfd)
+  if (serv->sfd && serv->sfd->fd != -1)
     return serv->sfd->fd;
 
   /* existing suitable random port socket linked to this transaction? */
   for (rfl = *fdlp; rfl; rfl = rfl->next)
-    if (server_isequal(serv, rfl->rfd->serv))
+    if (rfl->rfd->family == serv->addr.sa.sa_family &&
+	rfl->rfd->sfd == serv->sfd)
       return rfl->rfd->fd;
 
   /* No. need new link. */
@@ -2224,7 +2215,8 @@ int allocate_rfd(struct randfd_list **fdlp, struct server *serv)
 	if ((fd = random_sock(serv)) != -1)
     	  {
 	    rfd = &daemon->randomsocks[i];
-	    rfd->serv = serv;
+	    rfd->sfd = serv->sfd;
+	    rfd->family = serv->addr.sa.sa_family;
 	    rfd->fd = fd;
 	    rfd->refcount = 1;
 	  }
@@ -2237,7 +2229,8 @@ int allocate_rfd(struct randfd_list **fdlp, struct server *serv)
       {
 	i = (j + finger) % RANDOM_SOCKS;
 	if (daemon->randomsocks[i].refcount != 0 &&
-	    server_isequal(serv, daemon->randomsocks[i].serv) &&
+	    serv->addr.sa.sa_family == daemon->randomsocks[i].family &&
+	    serv->sfd == daemon->randomsocks[i].sfd &&
 	    daemon->randomsocks[i].refcount != 0xfffe)
 	  {
 	    finger = i + 1;
@@ -2527,18 +2520,11 @@ void resend_query()
 void server_gone(struct server *server)
 {
   struct frec *f;
-  int i;
 
   for (f = daemon->frec_list; f; f = f->next)
     if (f->sentto && f->sentto == server)
       free_frec(f);
 
-  /* If any random socket refers to this server, NULL the reference.
-     No more references to the socket will be created in the future. */
-  for (i = 0; i < RANDOM_SOCKS; i++)
-    if (daemon->randomsocks[i].refcount != 0 && daemon->randomsocks[i].serv == server)
-      daemon->randomsocks[i].serv = NULL;
-  
   if (daemon->last_server == server)
     daemon->last_server = NULL;
 

src/network.c

@@ -1378,11 +1378,29 @@ int local_bind(int fd, union mysockaddr *addr, char *intname, unsigned int ifind
   return 1;
 }
 
+static int allocate_sfd_socket(union mysockaddr *addr, char *intname, unsigned int ifindex)
+{
+  int fd;
+  int opt = 1;
+
+  if ((fd = socket(addr->sa.sa_family, SOCK_DGRAM, 0)) == -1)
+    return -1;
+
+  if ((addr->sa.sa_family == AF_INET6 && setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &opt, sizeof(opt)) == -1) ||
+      !local_bind(fd, addr, intname, ifindex, 0) || !fix_fd(fd))
+    { 
+      int errsave = errno; /* save error from bind/setsockopt. */
+      close(fd);
+      errno = errsave;
+      return -1;
+    }
+  return fd;
+}
+
 static struct serverfd *allocate_sfd(union mysockaddr *addr, char *intname, unsigned int ifindex)
 {
   struct serverfd *sfd;
-  int errsave;
-  int opt = 1;
+  int singlefd = 1;
 
   /* when using random ports, servers which would otherwise use
      the INADDR_ANY/port0 socket have sfd set to NULL, this is 
@@ -1391,13 +1409,15 @@ static struct serverfd *allocate_sfd(union mysockaddr *addr, char *intname, unsi
     {
       errno = 0;
 
-      if (addr->sa.sa_family == AF_INET &&
-	  addr->in.sin_port == htons(0)) 
-	return NULL;
-
-      if (addr->sa.sa_family == AF_INET6 &&
-	  addr->in6.sin6_port == htons(0)) 
-	return NULL;
+      if ((addr->sa.sa_family == AF_INET &&
+	  addr->in.sin_port == htons(0)) ||
+	  (addr->sa.sa_family == AF_INET6 &&
+	  addr->in6.sin6_port == htons(0)))
+	{
+	  if (intname[0] == 0)
+	    return NULL;
+	  singlefd = 0;
+	}
     }
 
   /* may have a suitable one already */
@@ -1411,21 +1431,16 @@ static struct serverfd *allocate_sfd(union mysockaddr *addr, char *intname, unsi
   errno = ENOMEM; /* in case malloc fails. */
   if (!(sfd = whine_malloc(sizeof(struct serverfd))))
     return NULL;
-  
-  if ((sfd->fd = socket(addr->sa.sa_family, SOCK_DGRAM, 0)) == -1)
-    {
-      free(sfd);
-      return NULL;
-    }
 
-  if ((addr->sa.sa_family == AF_INET6 && setsockopt(sfd->fd, IPPROTO_IPV6, IPV6_V6ONLY, &opt, sizeof(opt)) == -1) ||
-      !local_bind(sfd->fd, addr, intname, ifindex, 0) || !fix_fd(sfd->fd))
-    { 
-      errsave = errno; /* save error from bind/setsockopt. */
-      close(sfd->fd);
-      free(sfd);
-      errno = errsave;
-      return NULL;
+  sfd->fd = -1;
+  if (singlefd)
+    {
+      sfd->fd = allocate_sfd_socket(addr, intname, ifindex);
+      if (sfd->fd == -1)
+	{
+	  free(sfd);
+	  return NULL;
+	}
     }
 
   safe_strncpy(sfd->interface, intname, sizeof(sfd->interface)); 
@@ -1607,6 +1622,27 @@ void add_update_server(int flags,
     }
 }
 
+static void free_sfd(struct serverfd *sfd)
+{
+  int i;
+  struct randfd_list *rl;
+
+  /* If any random socket refers to this serverfd, invalidate the reference.
+  NULL is valid value in randfd.sfd, cannot use that. */
+  for (i = 0; i < RANDOM_SOCKS; i++)
+    if (daemon->randomsocks[i].refcount != 0 && daemon->randomsocks[i].sfd == sfd)
+      daemon->randomsocks[i].sfd = SERVERFD_INVALID;
+  for (rl = daemon->rfl_poll; rl; rl = rl->next)
+    /* Invalidate sfd pointer so it is no longer reused.
+     * Pending answers might be still received and processed. */
+    if (rl->rfd->sfd == sfd)
+      rl->rfd->sfd = SERVERFD_INVALID;
+
+  if (sfd->fd != -1)
+    close(sfd->fd);
+  free(sfd);
+}
+
 void check_servers(void)
 {
   struct irec *iface;
@@ -1747,8 +1783,7 @@ void check_servers(void)
        if (!sfd->used) 
 	{
 	  *up = sfd->next;
-	  close(sfd->fd);
-	  free(sfd);
+	  free_sfd(sfd);
 	} 
       else
 	up = &sfd->next;