Use poll() instead of select() to remove limits on open file descriptors.

CHANGELOG

@@ -1,3 +1,11 @@
+version 2.74
+            Fix reversion in 2.73 where --conf-file would attempt to
+	    read the default file, rather than no file.
+
+	    Fix inotify code to handle dangling symlinks better and
+	    not SEGV in some circumstances.
+
+
 version 2.73
             Fix crash at startup when an empty suffix is supplied to
 	    --conf-dir, also trivial memory leak. Thanks to 

Makefile

@@ -73,7 +73,7 @@ objs = cache.o rfc1035.o util.o option.o forward.o network.o \
        dnsmasq.o dhcp.o lease.o rfc2131.o netlink.o dbus.o bpf.o \
        helper.o tftp.o log.o conntrack.o dhcp6.o rfc3315.o \
        dhcp-common.o outpacket.o radv.o slaac.o auth.o ipset.o \
-       domain.o dnssec.o blockdata.o tables.o loop.o inotify.o
+       domain.o dnssec.o blockdata.o tables.o loop.o inotify.o poll.o
 
 hdrs = dnsmasq.h config.h dhcp-protocol.h dhcp6-protocol.h \
        dns-protocol.h radv-protocol.h ip6addr.h

bld/Android.mk

@@ -10,7 +10,7 @@ LOCAL_SRC_FILES :=  bpf.c cache.c dbus.c dhcp.c dnsmasq.c \
 		    dhcp6.c rfc3315.c dhcp-common.c outpacket.c \
 		    radv.c slaac.c auth.c ipset.c domain.c \
 	            dnssec.c dnssec-openssl.c blockdata.c tables.c \
-		    loop.c inotify.c
+		    loop.c inotify.c poll.c
 
 LOCAL_MODULE := dnsmasq
 

debian/changelog

@@ -1,3 +1,15 @@
+dnsmasq (2.74-1) unstable; urgency=low
+
+   * New upstream. 
+	
+ -- Simon Kelley <simon@thekelleys.org.uk>  Thu, 7 Jul 2015 21:54:11 +0000
+
+dnsmasq (2.73-2) unstable; urgency=low
+
+   * Fix behaviour of empty --conf-file (closes: #790341)
+
+ -- Simon Kelley <simon@thekelleys.org.uk>  Thu, 7 Jul 2015 21:46:42 +0000
+
 dnsmasq (2.73-1) unstable; urgency=low
 
    * New upstream. (closes: #786996)

man/dnsmasq.8

@@ -654,7 +654,7 @@ Provide DS records to act a trust anchors for DNSSEC
 validation. Typically these will be the DS record(s) for Zone Signing
 key(s) of the root zone,
 but trust anchors for limited domains are also possible. The current
-root-zone trust anchors may be donwloaded from https://data.iana.org/root-anchors/root-anchors.xml 
+root-zone trust anchors may be downloaded from https://data.iana.org/root-anchors/root-anchors.xml 
 .TP
 .B --dnssec-check-unsigned
 As a default, dnsmasq does not check that unsigned DNS replies are

src/dbus.c

@@ -749,8 +749,7 @@ char *dbus_init(void)
 }
  
 
-void set_dbus_listeners(int *maxfdp,
+void set_dbus_listeners(void)
-			fd_set *rset, fd_set *wset, fd_set *eset)
 {
   struct watch *w;
   
@@ -760,19 +759,17 @@ void set_dbus_listeners(int *maxfdp,
 	unsigned int flags = dbus_watch_get_flags(w->watch);
 	int fd = dbus_watch_get_unix_fd(w->watch);
 	
-	bump_maxfd(fd, maxfdp);
-	
 	if (flags & DBUS_WATCH_READABLE)
-	  FD_SET(fd, rset);
+	  poll_listen(fd, POLLIN);
 	
 	if (flags & DBUS_WATCH_WRITABLE)
-	  FD_SET(fd, wset);
+	  poll_listen(fd, POLLOUT);
 	
-	FD_SET(fd, eset);
+	poll_listen(fd, POLLERR);
       }
 }
 
-void check_dbus_listeners(fd_set *rset, fd_set *wset, fd_set *eset)
+void check_dbus_listeners()
 {
   DBusConnection *connection = (DBusConnection *)daemon->dbus;
   struct watch *w;
@@ -783,13 +780,13 @@ void check_dbus_listeners(fd_set *rset, fd_set *wset, fd_set *eset)
 	unsigned int flags = 0;
 	int fd = dbus_watch_get_unix_fd(w->watch);
 	
-	if (FD_ISSET(fd, rset))
+	if (poll_check(fd, POLLIN))
 	  flags |= DBUS_WATCH_READABLE;
 	
-	if (FD_ISSET(fd, wset))
+	if (poll_check(fd, POLLOUT))
 	  flags |= DBUS_WATCH_WRITABLE;
 	
-	if (FD_ISSET(fd, eset))
+	if (poll_check(fd, POLLERR))
 	  flags |= DBUS_WATCH_ERROR;
 
 	if (flags != 0)

src/dnsmasq.c

@@ -24,8 +24,8 @@ struct daemon *daemon;
 static volatile pid_t pid = 0;
 static volatile int pipewrite;
 
-static int set_dns_listeners(time_t now, fd_set *set, int *maxfdp);
+static int set_dns_listeners(time_t now);
-static void check_dns_listeners(fd_set *set, time_t now);
+static void check_dns_listeners(time_t now);
 static void sig_handler(int sig);
 static void async_event(int pipe, time_t now);
 static void fatal_event(struct event_desc *ev, char *msg);
@@ -799,10 +799,6 @@ int main (int argc, char **argv)
   if (option_bool(OPT_TFTP))
     {
       struct tftp_prefix *p;
-#ifdef FD_SETSIZE
-      if (FD_SETSIZE < (unsigned)max_fd)
-	max_fd = FD_SETSIZE;
-#endif
 
       my_syslog(MS_TFTP | LOG_INFO, "TFTP %s%s %s", 
 		daemon->tftp_prefix ? _("root is ") : _("enabled"),
@@ -862,88 +858,58 @@ int main (int argc, char **argv)
   
   while (1)
     {
-      int maxfd = -1;
+      int t, timeout = -1;
-      struct timeval t, *tp = NULL;
-      fd_set rset, wset, eset;
       
-      FD_ZERO(&rset);
+      poll_reset();
-      FD_ZERO(&wset);
-      FD_ZERO(&eset);
       
       /* if we are out of resources, find how long we have to wait
 	 for some to come free, we'll loop around then and restart
 	 listening for queries */
-      if ((t.tv_sec = set_dns_listeners(now, &rset, &maxfd)) != 0)
+      if ((t = set_dns_listeners(now)) != 0)
-	{
+	timeout = t * 1000;
-	  t.tv_usec = 0;
-	  tp = &t;
-	}
 
       /* Whilst polling for the dbus, or doing a tftp transfer, wake every quarter second */
       if (daemon->tftp_trans ||
 	  (option_bool(OPT_DBUS) && !daemon->dbus))
-	{
+	timeout = 250;
-	  t.tv_sec = 0;
+
-	  t.tv_usec = 250000;
-	  tp = &t;
-	}
       /* Wake every second whilst waiting for DAD to complete */
       else if (is_dad_listeners())
-	{
+	timeout = 1000;
-	  t.tv_sec = 1;
-	  t.tv_usec = 0;
-	  tp = &t;
-	}
 
 #ifdef HAVE_DBUS
-      set_dbus_listeners(&maxfd, &rset, &wset, &eset);
+      set_dbus_listeners();
 #endif	
   
 #ifdef HAVE_DHCP
       if (daemon->dhcp || daemon->relay4)
 	{
-	  FD_SET(daemon->dhcpfd, &rset);
+	  poll_listen(daemon->dhcpfd, POLLIN);
-	  bump_maxfd(daemon->dhcpfd, &maxfd);
 	  if (daemon->pxefd != -1)
-	    {
+	    poll_listen(daemon->pxefd, POLLIN);
-	      FD_SET(daemon->pxefd, &rset);
-	      bump_maxfd(daemon->pxefd, &maxfd);
-	    }
 	}
 #endif
 
 #ifdef HAVE_DHCP6
       if (daemon->doing_dhcp6 || daemon->relay6)
-	{
+	poll_listen(daemon->dhcp6fd, POLLIN);
-	  FD_SET(daemon->dhcp6fd, &rset);
-	  bump_maxfd(daemon->dhcp6fd, &maxfd);
-	}
 	
       if (daemon->doing_ra)
-	{
+	poll_listen(daemon->icmp6fd, POLLIN); 
-	  FD_SET(daemon->icmp6fd, &rset);
-	  bump_maxfd(daemon->icmp6fd, &maxfd); 
-	}
 #endif
     
 #ifdef HAVE_INOTIFY
       if (daemon->inotifyfd != -1)
-	{
+	poll_listen(daemon->inotifyfd, POLLIN);
-	  FD_SET(daemon->inotifyfd, &rset);
-	  bump_maxfd(daemon->inotifyfd, &maxfd);
-	}
 #endif
 
 #if defined(HAVE_LINUX_NETWORK)
-      FD_SET(daemon->netlinkfd, &rset);
+      poll_listen(daemon->netlinkfd, POLLIN);
-      bump_maxfd(daemon->netlinkfd, &maxfd);
 #elif defined(HAVE_BSD_NETWORK)
-      FD_SET(daemon->routefd, &rset);
+      poll_listen(daemon->routefd, POLLIN);
-      bump_maxfd(daemon->routefd, &maxfd);
 #endif
       
-      FD_SET(piperead, &rset);
+      poll_listen(piperead, POLLIN);
-      bump_maxfd(piperead, &maxfd);
 
 #ifdef HAVE_DHCP
 #  ifdef HAVE_SCRIPT
@@ -954,10 +920,7 @@ int main (int argc, char **argv)
 #    endif
 
       if (!helper_buf_empty())
-	{
+	poll_listen(daemon->helperfd, POLLOUT);
-	  FD_SET(daemon->helperfd, &wset);
-	  bump_maxfd(daemon->helperfd, &maxfd);
-	}
 #  else
       /* need this for other side-effects */
       while (do_script_run(now));
@@ -971,17 +934,14 @@ int main (int argc, char **argv)
    
       /* must do this just before select(), when we know no
 	 more calls to my_syslog() can occur */
-      set_log_writer(&wset, &maxfd);
+      set_log_writer();
       
-      if (select(maxfd+1, &rset, &wset, &eset, tp) < 0)
+      if (do_poll(timeout) < 0)
-	{
+	continue;
-	  /* otherwise undefined after error */
-	  FD_ZERO(&rset); FD_ZERO(&wset); FD_ZERO(&eset);
-	}
       
       now = dnsmasq_time();
 
-      check_log_writer(&wset);
+      check_log_writer(0);
 
       /* prime. */
       enumerate_interfaces(1);
@@ -997,15 +957,15 @@ int main (int argc, char **argv)
 	}
 
 #if defined(HAVE_LINUX_NETWORK)
-      if (FD_ISSET(daemon->netlinkfd, &rset))
+      if (poll_check(daemon->netlinkfd, POLLIN))
 	netlink_multicast();
 #elif defined(HAVE_BSD_NETWORK)
-      if (FD_ISSET(daemon->routefd, &rset))
+      if (poll_check(daemon->routefd, POLLIN))
 	route_sock();
 #endif
 
 #ifdef HAVE_INOTIFY
-      if  (daemon->inotifyfd != -1 && FD_ISSET(daemon->inotifyfd, &rset) && inotify_check(now))
+      if  (daemon->inotifyfd != -1 && poll_check(daemon->inotifyfd, POLLIN) && inotify_check(now))
 	{
 	  if (daemon->port != 0 && !option_bool(OPT_NO_POLL))
 	    poll_resolv(1, 1, now);
@@ -1025,7 +985,7 @@ int main (int argc, char **argv)
 	}
 #endif
 
-      if (FD_ISSET(piperead, &rset))
+      if (poll_check(piperead, POLLIN))
 	async_event(piperead, now);
       
 #ifdef HAVE_DBUS
@@ -1038,34 +998,34 @@ int main (int argc, char **argv)
 	  if (daemon->dbus)
 	    my_syslog(LOG_INFO, _("connected to system DBus"));
 	}
-      check_dbus_listeners(&rset, &wset, &eset);
+      check_dbus_listeners();
 #endif
       
-      check_dns_listeners(&rset, now);
+      check_dns_listeners(now);
 
 #ifdef HAVE_TFTP
-      check_tftp_listeners(&rset, now);
+      check_tftp_listeners(now);
 #endif      
 
 #ifdef HAVE_DHCP
       if (daemon->dhcp || daemon->relay4)
 	{
-	  if (FD_ISSET(daemon->dhcpfd, &rset))
+	  if (poll_check(daemon->dhcpfd, POLLIN))
 	    dhcp_packet(now, 0);
-	  if (daemon->pxefd != -1 && FD_ISSET(daemon->pxefd, &rset))
+	  if (daemon->pxefd != -1 && poll_check(daemon->pxefd, POLLIN))
 	    dhcp_packet(now, 1);
 	}
 
 #ifdef HAVE_DHCP6
-      if ((daemon->doing_dhcp6 || daemon->relay6) && FD_ISSET(daemon->dhcp6fd, &rset))
+      if ((daemon->doing_dhcp6 || daemon->relay6) && poll_check(daemon->dhcp6fd, POLLIN))
 	dhcp6_packet(now);
 
-      if (daemon->doing_ra && FD_ISSET(daemon->icmp6fd, &rset))
+      if (daemon->doing_ra && poll_check(daemon->icmp6fd, POLLIN))
 	icmp6_packet(now);
 #endif
 
 #  ifdef HAVE_SCRIPT
-      if (daemon->helperfd != -1 && FD_ISSET(daemon->helperfd, &wset))
+      if (daemon->helperfd != -1 && poll_check(daemon->helperfd, POLLIN))
 	helper_write();
 #  endif
 #endif
@@ -1470,7 +1430,7 @@ void clear_cache_and_reload(time_t now)
 #endif
 }
 
-static int set_dns_listeners(time_t now, fd_set *set, int *maxfdp)
+static int set_dns_listeners(time_t now)
 {
   struct serverfd *serverfdp;
   struct listener *listener;
@@ -1482,8 +1442,7 @@ static int set_dns_listeners(time_t now, fd_set *set, int *maxfdp)
   for (transfer = daemon->tftp_trans; transfer; transfer = transfer->next)
     {
       tftp++;
-      FD_SET(transfer->sockfd, set);
+      poll_listen(transfer->sockfd, POLLIN);
-      bump_maxfd(transfer->sockfd, maxfdp);
     }
 #endif
   
@@ -1492,27 +1451,18 @@ static int set_dns_listeners(time_t now, fd_set *set, int *maxfdp)
     get_new_frec(now, &wait, 0);
   
   for (serverfdp = daemon->sfds; serverfdp; serverfdp = serverfdp->next)
-    {
+    poll_listen(serverfdp->fd, POLLIN);
-      FD_SET(serverfdp->fd, set);
-      bump_maxfd(serverfdp->fd, maxfdp);
-    }
     
   if (daemon->port != 0 && !daemon->osport)
     for (i = 0; i < RANDOM_SOCKS; i++)
       if (daemon->randomsocks[i].refcount != 0)
-	{
+	poll_listen(daemon->randomsocks[i].fd, POLLIN);
-	  FD_SET(daemon->randomsocks[i].fd, set);
-	  bump_maxfd(daemon->randomsocks[i].fd, maxfdp);
-	}
 	  
   for (listener = daemon->listeners; listener; listener = listener->next)
     {
       /* only listen for queries if we have resources */
       if (listener->fd != -1 && wait == 0)
-	{
+	poll_listen(listener->fd, POLLIN);
-	  FD_SET(listener->fd, set);
-	  bump_maxfd(listener->fd, maxfdp);
-	}
 	
       /* death of a child goes through the select loop, so
 	 we don't need to explicitly arrange to wake up here */
@@ -1520,17 +1470,13 @@ static int set_dns_listeners(time_t now, fd_set *set, int *maxfdp)
 	for (i = 0; i < MAX_PROCS; i++)
 	  if (daemon->tcp_pids[i] == 0)
 	    {
-	      FD_SET(listener->tcpfd, set);
+	      poll_listen(listener->tcpfd, POLLIN);
-	      bump_maxfd(listener->tcpfd, maxfdp);
 	      break;
 	    }
 
 #ifdef HAVE_TFTP
       if (tftp <= daemon->tftp_max && listener->tftpfd != -1)
-	{
+	poll_listen(listener->tftpfd, POLLIN);
-	  FD_SET(listener->tftpfd, set);
-	  bump_maxfd(listener->tftpfd, maxfdp);
-	}
 #endif
 
     }
@@ -1538,33 +1484,33 @@ static int set_dns_listeners(time_t now, fd_set *set, int *maxfdp)
   return wait;
 }
 
-static void check_dns_listeners(fd_set *set, time_t now)
+static void check_dns_listeners(time_t now)
 {
   struct serverfd *serverfdp;
   struct listener *listener;
   int i;
 
   for (serverfdp = daemon->sfds; serverfdp; serverfdp = serverfdp->next)
-    if (FD_ISSET(serverfdp->fd, set))
+    if (poll_check(serverfdp->fd, POLLIN))
       reply_query(serverfdp->fd, serverfdp->source_addr.sa.sa_family, now);
   
   if (daemon->port != 0 && !daemon->osport)
     for (i = 0; i < RANDOM_SOCKS; i++)
       if (daemon->randomsocks[i].refcount != 0 && 
-	  FD_ISSET(daemon->randomsocks[i].fd, set))
+	  poll_check(daemon->randomsocks[i].fd, POLLIN))
 	reply_query(daemon->randomsocks[i].fd, daemon->randomsocks[i].family, now);
   
   for (listener = daemon->listeners; listener; listener = listener->next)
     {
-      if (listener->fd != -1 && FD_ISSET(listener->fd, set))
+      if (listener->fd != -1 && poll_check(listener->fd, POLLIN))
 	receive_query(listener, now); 
       
 #ifdef HAVE_TFTP     
-      if (listener->tftpfd != -1 && FD_ISSET(listener->tftpfd, set))
+      if (listener->tftpfd != -1 && poll_check(listener->tftpfd, POLLIN))
 	tftp_request(listener, now);
 #endif
 
-      if (listener->tcpfd != -1 && FD_ISSET(listener->tcpfd, set))
+      if (listener->tcpfd != -1 && poll_check(listener->tcpfd, POLLIN))
 	{
 	  int confd, client_ok = 1;
 	  struct irec *iface = NULL;
@@ -1755,14 +1701,22 @@ int icmp_ping(struct in_addr addr)
      better not use any resources our caller has in use...)
      but we remain deaf to signals or further DHCP packets. */
 
-  int fd;
+  /* There can be a problem using dnsmasq_time() to end the loop, since
+     it's not monotonic, and can go backwards if the system clock is
+     tweaked, leading to the code getting stuck in this loop and
+     ignoring DHCP requests. To fix this, we check to see if select returned
+     as a result of a timeout rather than a socket becoming available. We
+     only allow this to happen as many times as it takes to get to the wait time
+     in quarter-second chunks. This provides a fallback way to end loop. */ 
+
+  int fd, rc;
   struct sockaddr_in saddr;
   struct { 
     struct ip ip;
     struct icmp icmp;
   } packet;
   unsigned short id = rand16();
-  unsigned int i, j;
+  unsigned int i, j, timeout_count;
   int gotreply = 0;
   time_t start, now;
 
@@ -1794,53 +1748,44 @@ int icmp_ping(struct in_addr addr)
   while (retry_send(sendto(fd, (char *)&packet.icmp, sizeof(struct icmp), 0, 
 			   (struct sockaddr *)&saddr, sizeof(saddr))));
   
-  for (now = start = dnsmasq_time(); 
+  for (now = start = dnsmasq_time(), timeout_count = 0; 
-       difftime(now, start) < (float)PING_WAIT;)
+       (difftime(now, start) < (float)PING_WAIT) && (timeout_count < PING_WAIT * 4);)
     {
-      struct timeval tv;
-      fd_set rset, wset;
       struct sockaddr_in faddr;
-      int maxfd = fd; 
       socklen_t len = sizeof(faddr);
       
-      tv.tv_usec = 250000;
+      poll_reset();
-      tv.tv_sec = 0; 
+      poll_listen(fd, POLLIN);
-      
+      set_dns_listeners(now);
-      FD_ZERO(&rset);
+      set_log_writer();
-      FD_ZERO(&wset);
-      FD_SET(fd, &rset);
-      set_dns_listeners(now, &rset, &maxfd);
-      set_log_writer(&wset, &maxfd);
       
 #ifdef HAVE_DHCP6
       if (daemon->doing_ra)
-	{
+	poll_listen(daemon->icmp6fd, POLLIN); 
-	  FD_SET(daemon->icmp6fd, &rset);
-	  bump_maxfd(daemon->icmp6fd, &maxfd); 
-	}
 #endif
       
-      if (select(maxfd+1, &rset, &wset, NULL, &tv) < 0)
+      rc = do_poll(250);
-	{
+      
-	  FD_ZERO(&rset);
+      if (rc < 0)
-	  FD_ZERO(&wset);
+	continue;
-	}
+      else if (rc == 0)
+	timeout_count++;
 
       now = dnsmasq_time();
 
-      check_log_writer(&wset);
+      check_log_writer(0);
-      check_dns_listeners(&rset, now);
+      check_dns_listeners(now);
 
 #ifdef HAVE_DHCP6
-      if (daemon->doing_ra && FD_ISSET(daemon->icmp6fd, &rset))
+      if (daemon->doing_ra && poll_check(daemon->icmp6fd, POLLIN))
 	icmp6_packet(now);
 #endif
       
 #ifdef HAVE_TFTP
-      check_tftp_listeners(&rset, now);
+      check_tftp_listeners(now);
 #endif
 
-      if (FD_ISSET(fd, &rset) &&
+      if (poll_check(fd, POLLIN) &&
 	  recvfrom(fd, &packet, sizeof(packet), 0,
 		   (struct sockaddr *)&faddr, &len) == sizeof(packet) &&
 	  saddr.sin_addr.s_addr == faddr.sin_addr.s_addr &&

src/dnsmasq.h

@@ -82,7 +82,7 @@ typedef unsigned long long u64;
 #if defined(HAVE_SOLARIS_NETWORK)
 #  include <sys/sockio.h>
 #endif
-#include <sys/select.h>
+#include <sys/poll.h>
 #include <sys/wait.h>
 #include <sys/time.h>
 #include <sys/un.h>
@@ -1191,7 +1191,6 @@ int memcmp_masked(unsigned char *a, unsigned char *b, int len,
 		  unsigned int mask);
 int expand_buf(struct iovec *iov, size_t size);
 char *print_mac(char *buff, unsigned char *mac, int len);
-void bump_maxfd(int fd, int *max);
 int read_write(int fd, unsigned char *packet, int size, int rw);
 
 int wildcard_match(const char* wildcard, const char* match);
@@ -1202,8 +1201,8 @@ void die(char *message, char *arg1, int exit_code);
 int log_start(struct passwd *ent_pw, int errfd);
 int log_reopen(char *log_file);
 void my_syslog(int priority, const char *format, ...);
-void set_log_writer(fd_set *set, int *maxfdp);
+void set_log_writer(void);
-void check_log_writer(fd_set *set);
+void check_log_writer(int force);
 void flush_log(void);
 
 /* option.c */
@@ -1366,8 +1365,8 @@ int iface_enumerate(int family, void *parm, int (callback)());
 /* dbus.c */
 #ifdef HAVE_DBUS
 char *dbus_init(void);
-void check_dbus_listeners(fd_set *rset, fd_set *wset, fd_set *eset);
+void check_dbus_listeners(void);
-void set_dbus_listeners(int *maxfdp, fd_set *rset, fd_set *wset, fd_set *eset);
+void set_dbus_listeners(void);
 #  ifdef HAVE_DHCP
 void emit_dbus_signal(int action, struct dhcp_lease *lease, char *hostname);
 #  endif
@@ -1394,7 +1393,7 @@ int helper_buf_empty(void);
 /* tftp.c */
 #ifdef HAVE_TFTP
 void tftp_request(struct listener *listen, time_t now);
-void check_tftp_listeners(fd_set *rset, time_t now);
+void check_tftp_listeners(time_t now);
 int do_tftp_script_run(void);
 #endif
 
@@ -1511,3 +1510,10 @@ void inotify_dnsmasq_init();
 int inotify_check(time_t now);
 void set_dynamic_inotify(int flag, int total_size, struct crec **rhash, int revhashsz);
 #endif
+
+/* poll.c */
+void poll_reset(void);
+int poll_check(int fd, short event);
+void poll_listen(int fd, short event);
+int do_poll(int timeout);
+

src/forward.c

@@ -1887,7 +1887,7 @@ unsigned char *tcp_request(int confd, time_t now,
 			     dst_addr_4, netmask, now, &ad_question, &do_bit);
 	  
 	  /* Do this by steam now we're not in the select() loop */
-	  check_log_writer(NULL); 
+	  check_log_writer(1); 
 	  
 	  if (m == 0)
 	    {
@@ -2108,7 +2108,7 @@ unsigned char *tcp_request(int confd, time_t now,
 	    }
 	}
 	  
-      check_log_writer(NULL);
+      check_log_writer(1);
       
       *length = htons(m);
            

src/inotify.c

@@ -18,6 +18,7 @@
 #ifdef HAVE_INOTIFY
 
 #include <sys/inotify.h>
+#include <sys/param.h> /* For MAXSYMLINKS */
 
 /* the strategy is to set a inotify on the directories containing
    resolv files, for any files in the directory which are close-write 
@@ -35,10 +36,55 @@
 static char *inotify_buffer;
 #define INOTIFY_SZ (sizeof(struct inotify_event) + NAME_MAX + 1)
 
+/* If path is a symbolic link, return the path it
+   points to, made absolute if relative.
+   If path doesn't exist or is not a symlink, return NULL.
+   Return value is malloc'ed */
+static char *my_readlink(char *path)
+{
+  ssize_t rc, size = 64;
+  char *buf;
+
+  while (1)
+    {
+      buf = safe_malloc(size);
+      rc = readlink(path, buf, (size_t)size);
+      
+      if (rc == -1)
+	{
+	  /* Not link or doesn't exist. */
+	  if (errno == EINVAL || errno == ENOENT)
+	    return NULL;
+	  else
+	    die(_("cannot access path %s: %s"), path, EC_MISC);
+	}
+      else if (rc < size-1)
+	{
+	  char *d;
+	  
+	  buf[rc] = 0;
+	  if (buf[0] != '/' && ((d = strrchr(path, '/'))))
+	    {
+	      /* Add path to relative link */
+	      char *new_buf = safe_malloc((d - path) + strlen(buf) + 2);
+	      *(d+1) = 0;
+	      strcpy(new_buf, path);
+	      strcat(new_buf, buf);
+	      free(buf);
+	      buf = new_buf;
+	    }
+	  return buf;
+	}
+
+      /* Buffer too small, increase and retry */
+      size += 64;
+      free(buf);
+    }
+}
+
 void inotify_dnsmasq_init()
 {
   struct resolvc *res;
-
   inotify_buffer = safe_malloc(INOTIFY_SZ);
   daemon->inotifyfd = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
   
@@ -47,19 +93,22 @@ void inotify_dnsmasq_init()
   
   for (res = daemon->resolv_files; res; res = res->next)
     {
-      char *d = NULL, *path;
+      char *d, *new_path, *path = safe_malloc(strlen(res->name) + 1);
+      int links = MAXSYMLINKS;
 
-      if (!(path = realpath(res->name, NULL)))
+      strcpy(path, res->name);
+
+      /* Follow symlinks until we reach a non-symlink, or a non-existant file. */
+      while ((new_path = my_readlink(path)))
 	{
-	  /* realpath will fail if the file doesn't exist, but
+	  if (links-- == 0)
-	     dnsmasq copes with missing files, so fall back 
+	    die(_("too many symlinks following %s"), res->name, EC_MISC);
-	     and assume that symlinks are not in use in that case. */
+	  free(path);
-	  if (errno == ENOENT)
+	  path = new_path;
-	    path = res->name;
-	  else
-	    die(_("cannot cannonicalise resolv-file %s: %s"), res->name, EC_MISC); 
 	}
 
+      res->wd = -1;
+
       if ((d = strrchr(path, '/')))
 	{
 	  *d = 0; /* make path just directory */
@@ -70,10 +119,11 @@ void inotify_dnsmasq_init()
 	  
 	  if (res->wd == -1 && errno == ENOENT)
 	    die(_("directory %s for resolv-file is missing, cannot poll"), res->name, EC_MISC);
-	  
-	  if (res->wd == -1)
-	    die(_("failed to create inotify for %s: %s"), res->name, EC_MISC);
 	}	  
+	 
+      if (res->wd == -1)
+	die(_("failed to create inotify for %s: %s"), res->name, EC_MISC);
+	
     }
 }
 

src/log.c

@@ -421,18 +421,15 @@ void my_syslog(int priority, const char *format, ...)
     } 
 }
 
-void set_log_writer(fd_set *set, int *maxfdp)
+void set_log_writer(void)
 {
   if (entries && log_fd != -1 && connection_good)
-    {
+    poll_listen(log_fd, POLLOUT);
-      FD_SET(log_fd, set);
-      bump_maxfd(log_fd, maxfdp);
-    }
 }
 
-void check_log_writer(fd_set *set)
+void check_log_writer(int force)
 {
-  if (log_fd != -1 && (!set || FD_ISSET(log_fd, set)))
+  if (log_fd != -1 && (force || poll_check(log_fd, POLLOUT)))
     log_write();
 }
 

src/option.c

@@ -4371,7 +4371,7 @@ void read_opts(int argc, char **argv, char *compile_opts)
 {
   char *buff = opt_malloc(MAXDNAME);
   int option, conffile_opt = '7', testmode = 0;
-  char *arg, *conffile = NULL;
+  char *arg, *conffile = CONFFILE;
       
   opterr = 0;
 
@@ -4488,11 +4488,8 @@ void read_opts(int argc, char **argv, char *compile_opts)
   if (conffile)
     {
       one_file(conffile, conffile_opt);
-      free(conffile);
+      if (conffile_opt == 0)
-    }
+	free(conffile);
-  else
-    {
-      one_file(CONFFILE, conffile_opt);
     }
 
   /* port might not be known when the address is parsed - fill in here */

src/poll.c

@@ -0,0 +1,124 @@
+/* dnsmasq is Copyright (c) 2000-2015 Simon Kelley
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 dated June, 1991, or
+   (at your option) version 3 dated 29 June, 2007.
+ 
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+     
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "dnsmasq.h"
+
+/* Wrapper for poll(). Allocates and extends array of struct pollfds,
+   keeps them in fd order so that we can set and test conditions on
+   fd using a simple but efficient binary chop. */
+
+/* poll_reset()
+   poll_listen(fd, event)
+   .
+   .
+   poll_listen(fd, event);
+
+   hits = do_poll(timeout);
+
+   if (poll_check(fd, event)
+    .
+    .
+
+   if (poll_check(fd, event)
+    .
+    .
+
+    event is OR of POLLIN, POLLOUT, POLLERR, etc
+*/
+
+static struct pollfd *pollfds = NULL;
+static nfds_t nfds, arrsize = 0;
+
+/* Binary search. Returns either the pollfd with fd, or
+   if the fd doesn't match, or return equals nfds, the entry
+   to the left of which a new record should be inserted. */
+static nfds_t fd_search(int fd)
+{
+  nfds_t left, right, mid;
+  
+  if ((right = nfds) == 0)
+    return 0;
+  
+  left = 0;
+  
+  while (1)
+    {
+      if (right == left + 1)
+	return (pollfds[left].fd >= fd) ? left : right;
+      
+      mid = (left + right)/2;
+      
+      if (pollfds[mid].fd > fd)
+	right = mid;
+      else 
+	left = mid;
+    }
+}
+
+void poll_reset(void)
+{
+  nfds = 0;
+}
+
+int do_poll(int timeout)
+{
+  return poll(pollfds, nfds, timeout);
+}
+
+int poll_check(int fd, short event)
+{
+  nfds_t i = fd_search(fd);
+  
+  if (i < nfds && pollfds[i].fd == fd)
+    return pollfds[i].revents & event;
+
+  return 0;
+}
+
+void poll_listen(int fd, short event)
+{
+   nfds_t i = fd_search(fd);
+  
+   if (i < nfds && pollfds[i].fd == fd)
+     pollfds[i].events |= event;
+   else
+     {
+       if (arrsize != nfds)
+	 memmove(&pollfds[i+1], &pollfds[i], (nfds - i) * sizeof(struct pollfd));
+       else
+	 {
+	   /* Array too small, extend. */
+	   struct pollfd *new;
+	   arrsize += 64;
+	   
+	   if (!(new = whine_malloc(arrsize * sizeof(struct pollfd))))
+	     return;
+
+	   if (pollfds)
+	     {
+	       memcpy(new, pollfds, i * sizeof(struct pollfd));
+	       memcpy(&new[i+1], &pollfds[i], (nfds - i) * sizeof(struct pollfd));
+	       free(pollfds);
+	     }
+	   
+	   pollfds = new;
+	 }
+       
+       pollfds[i].fd = fd;
+       pollfds[i].events = event;
+       nfds++;
+     }
+}

src/tftp.c

@@ -502,7 +502,7 @@ static struct tftp_file *check_tftp_fileperm(ssize_t *len, char *prefix)
   return NULL;
 }
 
-void check_tftp_listeners(fd_set *rset, time_t now)
+void check_tftp_listeners(time_t now)
 {
   struct tftp_transfer *transfer, *tmp, **up;
   ssize_t len;
@@ -518,7 +518,7 @@ void check_tftp_listeners(fd_set *rset, time_t now)
       
       prettyprint_addr(&transfer->peer, daemon->addrbuff);
      
-      if (FD_ISSET(transfer->sockfd, rset))
+      if (poll_check(transfer->sockfd, POLLIN))
 	{
 	  /* we overwrote the buffer... */
 	  daemon->srv_save = NULL;

src/util.c

@@ -570,12 +570,6 @@ char *print_mac(char *buff, unsigned char *mac, int len)
   return buff;
 }
 
-void bump_maxfd(int fd, int *max)
-{
-  if (fd > *max)
-    *max = fd;
-}
-
 /* rc is return from sendto and friends.
    Return 1 if we should retry.
    Set errno to zero if we succeeded. */