Fix problems with ipset or nftset and TCP DNS transport.

If DNS is happening over TCP, the query is handled by a forked
process. Of ipset ot nftset is configured, this might include
inserting addresses in the *sets. Before this update, that
was done by the forked process using handles inherited from the
parent "master" process.

This is inherently racy. If the master process or another
child process tries to do updates at the same time, the
updates can clash and fail.

To see this, you need a busy server doing lots of DNS
queries over TCP, and ipset or nftset configured.

Going forward, we use the already established pipe to send the
updates from the child back to the master process, which
serialises them.

src/cache.c

@@ -864,6 +864,16 @@ void cache_update_hwm(void)
 }
 #endif
 
+#if defined(HAVE_IPSET) || defined(HAVE_NFTSET)
+void cache_send_ipset(unsigned char op, struct ipsets *sets, int flags, union all_addr *addr)
+{
+  read_write(daemon->pipe_to_parent, &op, sizeof(op), RW_WRITE);
+  read_write(daemon->pipe_to_parent, (unsigned char *)&sets, sizeof(sets), RW_WRITE);
+  read_write(daemon->pipe_to_parent, (unsigned char *)&flags, sizeof(flags), RW_WRITE);
+  read_write(daemon->pipe_to_parent, (unsigned char *)addr, sizeof(*addr), RW_WRITE);
+}
+#endif
+
 /* A marshalled cache entry arrives on fd, read, unmarshall and insert into cache of master process. */
 int cache_recv_insert(time_t now, int fd)
 {
@@ -1012,11 +1022,45 @@ int cache_recv_insert(time_t now, int fd)
 #endif
 	      crecp = really_insert(daemon->namebuff, &addr, class, now, ttl, flags);
 	    }
-
+	  
 	  /* loop reading RRs, since we don't want to go back to the poll() loop
 	     and start processing other queries which might pollute the insertion
 	     chain. The child will never block between the first OP_RR and the OP_END */
 	  continue;
+	  
+#if defined(HAVE_IPSET) || defined(HAVE_NFTSET)
+	case PIPE_OP_IPSET:
+	case PIPE_OP_NFTSET:
+	    {
+	      struct ipsets *sets;
+	      char **sets_cur;
+	      
+	      if (!read_write(fd, (unsigned char *)&sets, sizeof(sets), RW_READ) ||
+		  !read_write(fd, (unsigned char *)&flags, sizeof(flags), RW_READ) ||
+		  !read_write(fd, (unsigned char *)&addr, sizeof(addr), RW_READ))
+		return 0;
+	      
+	      for (sets_cur = sets->sets; *sets_cur; sets_cur++)
+		{
+		  int rc = -1;
+		  
+#ifdef HAVE_IPSET
+		  if (op == PIPE_OP_IPSET)
+		    rc = add_to_ipset(*sets_cur, &addr, flags, 0);
+#endif
+		  
+#ifdef HAVE_NFTSET		  
+		  if (op == PIPE_OP_NFTSET)
+		    rc = add_to_nftset(*sets_cur, &addr, flags, 0);
+#endif
+		  
+		  if (rc == 0)
+		    log_query((flags & (F_IPV4 | F_IPV6)) | F_IPSET, sets->domain, &addr, *sets_cur, op == PIPE_OP_IPSET);
+		}
+	      
+	      return 1;
+	    }
+#endif
 	}
     }
 }

src/config.h

@@ -153,6 +153,7 @@ NO_AUTH
 NO_DUMPFILE
 NO_LOOP
 NO_INOTIFY
+NO_IPSET
    these are available to explicitly disable compile time options which would 
    otherwise be enabled automatically or which are enabled  by default 
    in the distributed source tree. Building dnsmasq
@@ -287,7 +288,6 @@ HAVE_SOCKADDR_SA_LEN
 #define HAVE_BSD_NETWORK
 #define HAVE_GETOPT_LONG
 #define HAVE_SOCKADDR_SA_LEN
-#define NO_IPSET
 /* Define before sys/socket.h is included so we get socklen_t */
 #define _BSD_SOCKLEN_T_
 /* Select the RFC_3542 version of the IPv6 socket API. 
@@ -297,7 +297,6 @@ HAVE_SOCKADDR_SA_LEN
 #ifndef SOL_TCP
 #  define SOL_TCP IPPROTO_TCP
 #endif
-#define NO_IPSET
 
 #elif defined(__NetBSD__)
 #define HAVE_BSD_NETWORK
@@ -347,6 +346,11 @@ HAVE_SOCKADDR_SA_LEN
 #undef HAVE_AUTH
 #endif
 
+#if !defined(HAVE_LINUX_NETWORK)
+#undef HAVE_IPSET
+#undef HAVE_NFTSET
+#endif
+
 #if defined(NO_IPSET)
 #undef HAVE_IPSET
 #endif
@@ -460,4 +464,4 @@ static char *compile_opts =
 #endif
 "dumpfile";
 
-#endif /* defined(HAVE_DHCP) */
+#endif /* defined(DNSMASQ_COMPILE_OPTS) */

src/dnsmasq.h

@@ -539,8 +539,10 @@ struct crec {
 
 #define PIPE_OP_RR      1  /* Resource record */
 #define PIPE_OP_END     2  /* Cache entry complete: commit */
-#define PIPE_OP_RESULT  3  /* validation result. */
+#define PIPE_OP_RESULT  3  /* Validation result */
 #define PIPE_OP_STATS   4  /* Update parent's stats */
+#define PIPE_OP_IPSET   5  /* Update IPset */
+#define PIPE_OP_NFTSET  6  /* Update NFTset */
 
 /* struct sockaddr is not large enough to hold any address,
    and specifically not big enough to hold an IPv6 address.
@@ -1361,6 +1363,10 @@ int cache_recv_insert(time_t now, int fd);
 #ifdef HAVE_DNSSEC
 void cache_update_hwm(void);
 #endif
+#if defined(HAVE_IPSET) || defined(HAVE_NFTSET)
+void cache_send_ipset(unsigned char op, struct ipsets *sets,
+		      int flags, union all_addr *addr);
+#endif
 struct crec *cache_insert(char *name, union all_addr *addr, unsigned short class, 
 			  time_t now, unsigned long ttl, unsigned int flags);
 void cache_reload(void);

src/forward.c

@@ -704,16 +704,19 @@ static size_t process_reply(struct dns_header *header, time_t now, struct server
   (void)ad_reqd;
   (void)do_bit;
  
-#ifdef HAVE_IPSET
-  if (daemon->ipsets && extract_name(header, n, NULL, daemon->namebuff, EXTR_NAME_EXTRACT, 0))
-    ipsets = domain_find_sets(daemon->ipsets, daemon->namebuff);
+#if defined(HAVE_IPSET) || defined(HAVE_NFTSET)
+  if ((daemon->ipsets || daemon->nftsets) && extract_name(header, n, NULL, daemon->namebuff, EXTR_NAME_EXTRACT, 0))
+    {
+#  ifdef HAVE_IPSET
+      ipsets = domain_find_sets(daemon->ipsets, daemon->namebuff);
+#  endif
+      
+#  ifdef HAVE_NFTSET
+      nftsets = domain_find_sets(daemon->nftsets, daemon->namebuff);
+#  endif
+    }
 #endif
-
-#ifdef HAVE_NFTSET
-  if (daemon->nftsets && extract_name(header, n, NULL, daemon->namebuff, EXTR_NAME_EXTRACT, 0))
-    nftsets = domain_find_sets(daemon->nftsets, daemon->namebuff);
-#endif
-
+  
   if ((pheader = find_pseudoheader(header, n, &plen, &sizep, &is_sign, NULL)))
     {
       /* Get extended RCODE. */

src/ipset.c

@@ -16,7 +16,7 @@
 
 #include "dnsmasq.h"
 
-#if defined(HAVE_IPSET) && defined(HAVE_LINUX_NETWORK)
+#if defined(HAVE_IPSET)
 
 #include <string.h>
 #include <errno.h>

src/nftset.c

@@ -17,7 +17,7 @@
 
 #include "dnsmasq.h"
 
-#if defined (HAVE_NFTSET) && defined (HAVE_LINUX_NETWORK)
+#if defined (HAVE_NFTSET)
 
 #include <nftables/libnftables.h>
 

src/rfc1035.c

@@ -1057,19 +1057,34 @@ int extract_addresses(struct dns_header *header, size_t qlen, char *name, time_t
 			  private_net6(&addr.addr6, !option_bool(OPT_LOCAL_REBIND)))
 			return 1;
 		    }
-		  
+
+		  if (flags & (F_IPV4 | F_IPV6))
+		    {
+		      /* If we're a child process, send this to the parent,
+			 since the ipset and nfset access is not re-entrant. */
 #ifdef HAVE_IPSET
-		  if (ipsets && (flags & (F_IPV4 | F_IPV6)))
-		    for (ipsets_cur = ipsets->sets; *ipsets_cur; ipsets_cur++)
-		      if (add_to_ipset(*ipsets_cur, &addr, flags, 0) == 0)
-			log_query((flags & (F_IPV4 | F_IPV6)) | F_IPSET, ipsets->domain, &addr, *ipsets_cur, 1);
+		      if (ipsets)
+			{
+			  if (daemon->pipe_to_parent != -1)
+			    cache_send_ipset(PIPE_OP_IPSET, ipsets, flags, &addr);
+			  else
+			    for (ipsets_cur = ipsets->sets; *ipsets_cur; ipsets_cur++)
+			      if (add_to_ipset(*ipsets_cur, &addr, flags, 0) == 0)
+				log_query((flags & (F_IPV4 | F_IPV6)) | F_IPSET, ipsets->domain, &addr, *ipsets_cur, 1);
+			}
 #endif
 #ifdef HAVE_NFTSET
-		  if (nftsets && (flags & (F_IPV4 | F_IPV6)))
-		    for (nftsets_cur = nftsets->sets; *nftsets_cur; nftsets_cur++)
-		      if (add_to_nftset(*nftsets_cur, &addr, flags, 0) == 0)
-			log_query((flags & (F_IPV4 | F_IPV6)) | F_IPSET, nftsets->domain, &addr, *nftsets_cur, 0);
+		      if (nftsets)
+			{
+			  if (daemon->pipe_to_parent != -1)
+			    cache_send_ipset(PIPE_OP_NFTSET, nftsets, flags, &addr);
+			  else
+			    for (nftsets_cur = nftsets->sets; *nftsets_cur; nftsets_cur++)
+			      if (add_to_nftset(*nftsets_cur, &addr, flags, 0) == 0)
+				log_query((flags & (F_IPV4 | F_IPV6)) | F_IPSET, nftsets->domain, &addr, *nftsets_cur, 0);
+			}
 #endif
+		    }
 		}
 	      
 	      if (insert)