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

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
 

src/dbus.c

@@ -749,8 +749,7 @@ char *dbus_init(void)
 }
  
 
-void set_dbus_listeners(int *maxfdp,
-			fd_set *rset, fd_set *wset, fd_set *eset)
+void set_dbus_listeners(void)
 {
   struct watch *w;
   
@@ -761,16 +760,16 @@ void set_dbus_listeners(int *maxfdp,
 	int fd = dbus_watch_get_unix_fd(w->watch);
 	
 	if (flags & DBUS_WATCH_READABLE)
-	  bump_maxfd(rset, fd, maxfdp);
+	  poll_listen(fd, POLLIN);
 	
 	if (flags & DBUS_WATCH_WRITABLE)
-	  bump_maxfd(wset, fd, maxfdp);
+	  poll_listen(fd, POLLOUT);
 	
-	bump_maxfd(eset, fd, maxfdp);
+	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;
@@ -781,13 +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.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(fd_set *set, 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 check_log_writer(fd_set *set);
+void set_log_writer(void);
+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 set_dbus_listeners(int *maxfdp, fd_set *rset, fd_set *wset, fd_set *eset);
+void check_dbus_listeners(void);
+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/log.c

@@ -421,15 +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)
-    bump_maxfd(set, log_fd, maxfdp);
+    poll_listen(log_fd, POLLOUT);
 }
 
-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/poll.c

+/* 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

@@ -570,25 +570,6 @@ char *print_mac(char *buff, unsigned char *mac, int len)
   return buff;
 }
 
-void bump_maxfd(fd_set *set, int fd, int *max)
-{
-#ifdef FD_SETSIZE
-  if (fd >= FD_SETSIZE)
-    {
-      static int logged = 0;
-      if (!logged)
-	my_syslog(LOG_ERR, _("File descriptor overflows FD_SET"));
-      logged = 1;
-    }
-  else
- #endif
-    {
-      FD_SET(fd, set);
-      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. */