From 6d1edd8d32afe25ac280db8bfbcfee6629e3bc5e Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Mon, 21 Jun 2021 15:59:07 +0100
Subject: [PATCH] Use correct packet-size limit in make_local_answer()

---
 src/dnsmasq.h      | 2 +-
 src/domain-match.c | 6 +++---
 src/forward.c      | 5 +++--
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/dnsmasq.h b/src/dnsmasq.h
index 66fc988..b21fc17 100644
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -1749,7 +1749,7 @@ int lookup_domain(char *qdomain, int flags, int *lowout, int *highout);
 int filter_servers(int seed, int flags, int *lowout, int *highout);
 int is_local_answer(time_t now, int first, char *name);
 size_t make_local_answer(int flags, int gotname, size_t size, struct dns_header *header,
-			 char *name, int first, int last);
+			 char *name, char *limit, int first, int last);
 int server_samegroup(struct server *a, struct server *b);
 #ifdef HAVE_DNSSEC
 int dnssec_server(struct server *server, char *keyname, int *firstp, int *lastp);
diff --git a/src/domain-match.c b/src/domain-match.c
index 834daf5..ee457c0 100644
--- a/src/domain-match.c
+++ b/src/domain-match.c
@@ -335,7 +335,7 @@ int is_local_answer(time_t now, int first, char *name)
   return rc;
 }
 
-size_t make_local_answer(int flags, int gotname, size_t size, struct dns_header *header, char *name, int first, int last)
+size_t make_local_answer(int flags, int gotname, size_t size, struct dns_header *header, char *name, char *limit, int first, int last)
 {
   int trunc = 0;
   unsigned char *p;
@@ -361,7 +361,7 @@ size_t make_local_answer(int flags, int gotname, size_t size, struct dns_header
 	  addr.addr4 = srv->addr;
 	
 	header->ancount = htons(ntohs(header->ancount) + 1);
-	add_resource_record(header, ((char *)header) + 65536, &trunc, sizeof(struct dns_header), &p, daemon->local_ttl, NULL, T_A, C_IN, "4", &addr);
+	add_resource_record(header, limit, &trunc, sizeof(struct dns_header), &p, daemon->local_ttl, NULL, T_A, C_IN, "4", &addr);
 	log_query((flags | F_CONFIG | F_FORWARD) & ~F_IPV6, name, (union all_addr *)&addr, NULL);
       }
   
@@ -376,7 +376,7 @@ size_t make_local_answer(int flags, int gotname, size_t size, struct dns_header
 	  addr.addr6 = srv->addr;
 	
 	header->ancount = htons(ntohs(header->ancount) + 1);
-	add_resource_record(header, ((char *)header) + 65536, &trunc, sizeof(struct dns_header), &p, daemon->local_ttl, NULL, T_AAAA, C_IN, "6", &addr);
+	add_resource_record(header, limit, &trunc, sizeof(struct dns_header), &p, daemon->local_ttl, NULL, T_AAAA, C_IN, "6", &addr);
 	log_query((flags | F_CONFIG | F_FORWARD) & ~F_IPV4, name, (union all_addr *)&addr, NULL);
       }
 
diff --git a/src/forward.c b/src/forward.c
index 458f554..8ab6c4a 100644
--- a/src/forward.c
+++ b/src/forward.c
@@ -525,7 +525,7 @@ static int forward_query(int udpfd, union mysockaddr *udpaddr,
  reply:
   if (udpfd != -1)
     {
-      if (!(plen = make_local_answer(flags, gotname, plen, header, daemon->namebuff, first, last)))
+      if (!(plen = make_local_answer(flags, gotname, plen, header, daemon->namebuff, limit, first, last)))
 	return 0;
       
       if (oph)
@@ -2080,7 +2080,8 @@ unsigned char *tcp_request(int confd, time_t now,
       /* In case of local answer or no connections made. */
       if (m == 0)
 	{
-	  if (!(m = make_local_answer(flags, gotname, size, header, daemon->namebuff, first, last)))
+	  if (!(m = make_local_answer(flags, gotname, size, header, daemon->namebuff,
+				      ((char *) header) + 65536, first, last)))
 	    break;
 	  
 	  if (have_pseudoheader)