Fix DNS server fd garbage collection.

If we're talking to upstream servers from a fixed port, specified by query-port
we create the fds to do this once, before dropping root, so that ports <1024 can be used.

But we call check_servers() before reading /etc/resolv.conf, so if the only servers
are in resolv.conf, at that point there will be no servers, and the fds get garbage
collected away, only to be recreated (but without root) after we read /etc/resolv.conf

Make pre-allocated server fds immortal, to avoid this problem.

CHANGELOG

@@ -1,3 +1,8 @@
+version 2.80
+	Add support for RFC 4039 DHCP rapid commit. Thanks to Ashram Method
+	for the initial patch and motivation.
+
+
 version 2.79
 	Fix parsing of CNAME arguments, which are confused by extra spaces.
 	Thanks to Diego Aguirre for spotting the bug.

Makefile

@@ -100,7 +100,8 @@ clean : mostly_clean
 install : all install-common
 
 install-common :
-	$(INSTALL) -d $(DESTDIR)$(BINDIR) -d $(DESTDIR)$(MANDIR)/man8
+	$(INSTALL) -d $(DESTDIR)$(BINDIR)
+	$(INSTALL) -d $(DESTDIR)$(MANDIR)/man8
 	$(INSTALL) -m 644 $(MAN)/dnsmasq.8 $(DESTDIR)$(MANDIR)/man8 
 	$(INSTALL) -m 755 $(BUILDDIR)/dnsmasq $(DESTDIR)$(BINDIR)
 

debian/changelog

@@ -2,7 +2,7 @@ dnsmasq (2.79-1) unstable; urgency=low
 
    * New upstream. (closes: #888200)
    * Fix trust-anchor regex in init script. (closes: #884347)
-   * Fix exit code for dhcp_release6 (closes: #833596)
+   * Fix exit code for dhcp_release6 (closes: #883596)
    * Add project homepage to control file. (closes: #887764)
    * New binary package dnsmasq-base-lua, includes Lua support.
    * Remove hardwired shlibs dependency for libnettle 3.3 and

debian/lintian-override

@@ -0,0 +1,3 @@
+# dnsmasq-base and dnsmasq-base-lua are mutually exclusive and both
+# provide /usr/share/doc/dnsmasq-base
+dnsmasq-base-lua binary: usr-share-doc-symlink-without-dependency dnsmasq-base

debian/rules

@@ -217,9 +217,12 @@ else
 	rm -rf debian/trees/lua-base/usr/share/man
 endif
 	$(call add_files,debian/trees/lua-base)
+	install -m 755 -d debian/trees/lua-base/usr/share/lintian/overrides
+	install -m 644 debian/lintian-override debian/trees/lua-base/usr/share/lintian/overrides/dnsmasq-base-lua
 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
 	$(DEB_HOST_GNU_TYPE)-strip -R .note -R .comment debian/trees/lua-base/usr/sbin/dnsmasq
 endif
+	ln -s $(package) debian/trees/lua-base/usr/share/doc/dnsmasq-base-lua
 	cd debian/trees/lua-base && find . -type f ! -regex '.*DEBIAN/.*' -printf '%P\0' | LC_ALL=C sort -z | xargs -r0 md5sum > DEBIAN/md5sums
 	dpkg-shlibdeps --warnings=1 debian/trees/lua-base/usr/sbin/dnsmasq
 	dpkg-gencontrol $(PACKAGE_VERSION) -pdnsmasq-base-lua -Pdebian/trees/lua-base

dnsmasq.conf.example

@@ -547,6 +547,14 @@
 # http://www.isc.org/files/auth.html
 #dhcp-authoritative
 
+# Set the DHCP server to enable DHCPv4 Rapid Commit Option per RFC 4039.
+# In this mode it will respond to a DHCPDISCOVER message including a Rapid Commit
+# option with a DHCPACK including a Rapid Commit option and fully committed address
+# and configuration information. This must only be enabled if either the server is 
+# the only server for the subnet, or multiple servers are present and they each
+# commit a binding for all clients.
+#dhcp-rapid-commit
+
 # Run an executable when a DHCP lease is created or destroyed.
 # The arguments sent to the script are "add" or "del",
 # then the MAC address, the IP address and finally the hostname

man/dnsmasq.8

@@ -1452,6 +1452,13 @@ allows dnsmasq to rebuild its lease database without each client needing to
 reacquire a lease, if the database is lost. For DHCPv6 it sets the
 priority in replies to 255 (the maximum) instead of 0 (the minimum).
 .TP
+.B --dhcp-rapid-commit
+Enable DHCPv4 Rapid Commit Option specified in RFC 4039. When enabled, dnsmasq
+will respond to a DHCPDISCOVER message including a Rapid Commit
+option with a DHCPACK including a Rapid Commit option and fully committed
+address and configuration information. Should only be enabled if either the
+server is  the only server for the subnet, or multiple servers are present and they each commit a binding for all clients.
+.TP
 .B --dhcp-alternate-port[=<server port>[,<client port>]]
 (IPv4 only) Change the ports used for DHCP from the default. If this option is
 given alone, without arguments, it changes the ports used for DHCP

src/dhcp-common.c

@@ -556,6 +556,7 @@ static const struct opttab_t {
   { "nntp-server", 71, OT_ADDR_LIST }, 
   { "irc-server", 74, OT_ADDR_LIST }, 
   { "user-class", 77, 0 },
+  { "rapid-commit", 80, 0 },
   { "FQDN", 81, OT_INTERNAL },
   { "agent-id", 82, OT_INTERNAL },
   { "client-arch", 93, 2 | OT_DEC },

src/dhcp-protocol.h

@@ -54,6 +54,7 @@
 #define OPTION_SNAME             66
 #define OPTION_FILENAME          67
 #define OPTION_USER_CLASS        77
+#define OPTION_RAPID_COMMIT      80
 #define OPTION_CLIENT_FQDN       81
 #define OPTION_AGENT_ID          82
 #define OPTION_ARCH              93

src/dnsmasq.h

@@ -250,7 +250,8 @@ struct event_desc {
 #define OPT_MAC_B64        54
 #define OPT_MAC_HEX        55
 #define OPT_TFTP_APREF_MAC 56
-#define OPT_LAST           57
+#define OPT_RAPID_COMMIT   57
+#define OPT_LAST           58
 
 /* extra flags for my_syslog, we use a couple of facilities since they are known 
    not to occupy the same bits as priorities, no matter how syslog.h is set up. */
@@ -505,7 +506,7 @@ struct serverfd {
   int fd;
   union mysockaddr source_addr;
   char interface[IF_NAMESIZE+1];
-  unsigned int ifindex, used;
+  unsigned int ifindex, used, preallocated;
   struct serverfd *next;
 };
 

src/network.c

@@ -1234,6 +1234,7 @@ static struct serverfd *allocate_sfd(union mysockaddr *addr, char *intname)
   struct serverfd *sfd;
   unsigned int ifindex = 0;
   int errsave;
+  int opt = 1;
   
   /* when using random ports, servers which would otherwise use
      the INADDR_ANY/port0 socket have sfd set to NULL */
@@ -1275,9 +1276,10 @@ static struct serverfd *allocate_sfd(union mysockaddr *addr, char *intname)
       return NULL;
     }
 
-  if (!local_bind(sfd->fd, addr, intname, ifindex, 0) || !fix_fd(sfd->fd))
+  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. */
+      errsave = errno; /* save error from bind/setsockopt. */
       close(sfd->fd);
       free(sfd);
       errno = errsave;
@@ -1288,6 +1290,7 @@ static struct serverfd *allocate_sfd(union mysockaddr *addr, char *intname)
   sfd->source_addr = *addr;
   sfd->next = daemon->sfds;
   sfd->ifindex = ifindex;
+  sfd->preallocated = 0;
   daemon->sfds = sfd;
 
   return sfd; 
@@ -1298,6 +1301,7 @@ static struct serverfd *allocate_sfd(union mysockaddr *addr, char *intname)
 void pre_allocate_sfds(void)
 {
   struct server *srv;
+  struct serverfd *sfd;
   
   if (daemon->query_port != 0)
     {
@@ -1309,7 +1313,8 @@ void pre_allocate_sfds(void)
 #ifdef HAVE_SOCKADDR_SA_LEN
       addr.in.sin_len = sizeof(struct sockaddr_in);
 #endif
-      allocate_sfd(&addr, "");
+      if ((sfd = allocate_sfd(&addr, "")))
+	sfd->preallocated = 1;
 #ifdef HAVE_IPV6
       memset(&addr, 0, sizeof(addr));
       addr.in6.sin6_family = AF_INET6;
@@ -1318,7 +1323,8 @@ void pre_allocate_sfds(void)
 #ifdef HAVE_SOCKADDR_SA_LEN
       addr.in6.sin6_len = sizeof(struct sockaddr_in6);
 #endif
-      allocate_sfd(&addr, "");
+      if ((sfd = allocate_sfd(&addr, "")))
+	sfd->preallocated = 1;
 #endif
     }
   
@@ -1472,8 +1478,9 @@ void check_servers(void)
   if (!option_bool(OPT_NOWILD))
     enumerate_interfaces(0);
 
+  /* don't garbage collect pre-allocated sfds. */
   for (sfd = daemon->sfds; sfd; sfd = sfd->next)
-    sfd->used = 0;
+    sfd->used = sfd->preallocated;
 
   for (count = 0, serv = daemon->servers; serv; serv = serv->next)
     {

src/option.c

@@ -160,6 +160,7 @@ struct myoption {
 #define LOPT_DHCPTTL       348
 #define LOPT_TFTP_MTU      349
 #define LOPT_REPLY_DELAY   350
+#define LOPT_RAPID_COMMIT  351
  
 #ifdef HAVE_GETOPT_LONG
 static const struct option opts[] =  
@@ -325,6 +326,7 @@ static const struct myoption opts[] =
     { "script-arp", 0, 0, LOPT_SCRIPT_ARP },
     { "dhcp-ttl", 1, 0 , LOPT_DHCPTTL },
     { "dhcp-reply-delay", 1, 0, LOPT_REPLY_DELAY },
+    { "dhcp-rapid-commit", 0, 0, LOPT_RAPID_COMMIT },
     { NULL, 0, 0, 0 }
   };
 
@@ -497,6 +499,7 @@ static struct {
   { LOPT_IGNORE_ADDR, ARG_DUP, "<ipaddr>", gettext_noop("Ignore DNS responses containing ipaddr."), NULL }, 
   { LOPT_DHCPTTL, ARG_ONE, "<ttl>", gettext_noop("Set TTL in DNS responses with DHCP-derived addresses."), NULL }, 
   { LOPT_REPLY_DELAY, ARG_ONE, "<integer>", gettext_noop("Delay DHCP replies for at least number of seconds."), NULL },
+  { LOPT_RAPID_COMMIT, OPT_RAPID_COMMIT, NULL, gettext_noop("Enables DHCPv4 Rapid Commit option."), NULL },
   { 0, 0, NULL, NULL, NULL }
 }; 
 

src/rfc2131.c

@@ -75,7 +75,7 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
   struct dhcp_vendor *vendor;
   struct dhcp_mac *mac;
   struct dhcp_netid_list *id_list;
-  int clid_len = 0, ignore = 0, do_classes = 0, selecting = 0, pxearch = -1;
+  int clid_len = 0, ignore = 0, do_classes = 0, rapid_commit = 0, selecting = 0, pxearch = -1;
   struct dhcp_packet *mess = (struct dhcp_packet *)daemon->dhcp_packet.iov_base;
   unsigned char *end = (unsigned char *)(mess + 1); 
   unsigned char *real_end = (unsigned char *)(mess + 1); 
@@ -1073,6 +1073,13 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 
       log_tags(tagif_netid, ntohl(mess->xid));
       apply_delay(mess->xid, recvtime, tagif_netid);
+
+      if (option_bool(OPT_RAPID_COMMIT) && option_find(mess, sz, OPTION_RAPID_COMMIT, 0))
+	{
+	  rapid_commit = 1;
+	  goto rapid_commit;
+	}
+      
       log_packet("DHCPOFFER" , &mess->yiaddr, emac, emac_len, iface_name, NULL, NULL, mess->xid);
       
       time = calc_time(context, config, option_find(mess, sz, OPTION_LEASE_TIME, 4));
@@ -1086,6 +1093,7 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
       
       return dhcp_packet_size(mess, agent_id, real_end);
 	
+
     case DHCPREQUEST:
       if (ignore || have_config(config, CONFIG_DISABLE))
 	return 0;
@@ -1186,6 +1194,7 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 
       log_packet("DHCPREQUEST", &mess->yiaddr, emac, emac_len, iface_name, NULL, NULL, mess->xid);
       
+    rapid_commit:
       if (!message)
 	{
 	  struct dhcp_config *addr_config;
@@ -1256,7 +1265,11 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 
       if (message)
 	{
-	  log_packet("DHCPNAK", &mess->yiaddr, emac, emac_len, iface_name, NULL, message, mess->xid);
+	  log_packet(rapid_commit ? "NOANSWER" : "DHCPNAK", &mess->yiaddr, emac, emac_len, iface_name, NULL, message, mess->xid);
+
+	  /* rapid commit case: lease allocate failed but don't send DHCPNAK */
+	  if (rapid_commit)
+	    return 0;
 	  
 	  mess->yiaddr.s_addr = 0;
 	  clear_packet(mess, end);
@@ -1419,7 +1432,9 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 	  option_put(mess, end, OPTION_MESSAGE_TYPE, 1, DHCPACK);
 	  option_put(mess, end, OPTION_SERVER_IDENTIFIER, INADDRSZ, ntohl(server_id(context, override, fallback).s_addr));
 	  option_put(mess, end, OPTION_LEASE_TIME, 4, time);
-	  do_options(context, mess, end, req_options, hostname, get_domain(mess->yiaddr), 
+	  if (rapid_commit)
+	     option_put(mess, end, OPTION_RAPID_COMMIT, 0, 0);
+	   do_options(context, mess, end, req_options, hostname, get_domain(mess->yiaddr), 
 		     netid, subnet_addr, fqdn_flags, borken_opt, pxearch, uuid, vendor_class_len, now, time, fuzz);
 	}