resolved: if dns_packet_append_answer() fails count how many RRs were successfully added

This is useful later when handling the truncation case: if we can't add
all RRs we'd like to add we need to set the TC bit, but still report the
number of RRs we added (and not the number of RRs we would have liked to
add) to the packet.

4 files changed, 11 insertions, 9 deletions

diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index b75b77760a..59be55a0eb 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -1215,7 +1215,7 @@ int dns_packet_append_question(DnsPacket *p, DnsQuestion *q) {
         return 0;
 }
 
-int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a) {
+int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a, unsigned *completed) {
         DnsResourceRecord *rr;
         DnsAnswerFlags flags;
         int r;
@@ -1226,6 +1226,9 @@ int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a) {
                 r = dns_packet_append_rr(p, rr, flags, NULL, NULL);
                 if (r < 0)
                         return r;
+
+                if (completed)
+                        (*completed)++;
         }
 
         return 0;
diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
index 38b14b92f5..c63298d823 100644
--- a/src/resolve/resolved-dns-packet.h
+++ b/src/resolve/resolved-dns-packet.h
@@ -203,7 +203,7 @@ int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, const DnsAnsw
 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start);
 int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, bool include_rfc6975, int rcode, size_t *start);
 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
-int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
+int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a, unsigned *completed);
 
 int dns_packet_patch_max_udp_size(DnsPacket *p, uint16_t max_udp_size);
 int dns_packet_patch_ttls(DnsPacket *p, usec_t timestamp);
diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index 7db906b0ad..15a3120e1a 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -765,6 +765,7 @@ int dns_scope_make_reply_packet(
                 DnsPacket **ret) {
 
         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        unsigned n_answer = 0, n_soa = 0;
         int r;
 
         assert(s);
@@ -796,15 +797,15 @@ int dns_scope_make_reply_packet(
                 return r;
         DNS_PACKET_HEADER(p)->qdcount = htobe16(dns_question_size(q));
 
-        r = dns_packet_append_answer(p, answer);
+        r = dns_packet_append_answer(p, answer, &n_answer);
         if (r < 0)
                 return r;
-        DNS_PACKET_HEADER(p)->ancount = htobe16(dns_answer_size(answer));
+        DNS_PACKET_HEADER(p)->ancount = htobe16(n_answer);
 
-        r = dns_packet_append_answer(p, soa);
+        r = dns_packet_append_answer(p, soa, &n_soa);
         if (r < 0)
                 return r;
-        DNS_PACKET_HEADER(p)->arcount = htobe16(dns_answer_size(soa));
+        DNS_PACKET_HEADER(p)->arcount = htobe16(n_soa);
 
         *ret = TAKE_PTR(p);
 
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 8776edb57c..8b3cb7fe1f 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -1583,11 +1583,9 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
                 if (r < 0)
                         return r;
 
-                r = dns_packet_append_answer(p, answer);
+                r = dns_packet_append_answer(p, answer, &nscount);
                 if (r < 0)
                         return r;
-
-                nscount += dns_answer_size(answer);
         }
         DNS_PACKET_HEADER(p)->nscount = htobe16(nscount);