resolved: extend dns_packet_append_opt() so that it can set the extended rcode

We don't make use of this yet, but later work will.

3 files changed, 9 insertions, 6 deletions

diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index 32978eb924..2cf07a628b 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -676,13 +676,15 @@ fail:
 }
 
 /* Append the OPT pseudo-RR described in RFC6891 */
-int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start) {
+int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start) {
         size_t saved_size;
         int r;
 
         assert(p);
         /* we must never advertise supported packet size smaller than the legacy max */
         assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX);
+        assert(rcode >= 0);
+        assert(rcode <= _DNS_RCODE_MAX);
 
         if (p->opt_start != (size_t) -1)
                 return -EBUSY;
@@ -701,13 +703,13 @@ int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, si
         if (r < 0)
                 goto fail;
 
-        /* maximum udp packet that can be received */
+        /* class: maximum udp packet that can be received */
         r = dns_packet_append_uint16(p, max_udp_size, NULL);
         if (r < 0)
                 goto fail;
 
         /* extended RCODE and VERSION */
-        r = dns_packet_append_uint16(p, 0, NULL);
+        r = dns_packet_append_uint16(p, ((uint16_t) rcode & 0x0FF0) << 4, NULL);
         if (r < 0)
                 goto fail;
 
diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
index fe2b386297..1216bcb72d 100644
--- a/src/resolve/resolved-dns-packet.h
+++ b/src/resolve/resolved-dns-packet.h
@@ -182,7 +182,7 @@ int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonica
 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
-int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
+int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start);
 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
 int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
 
@@ -234,7 +234,8 @@ enum {
         DNS_RCODE_BADNAME = 20,
         DNS_RCODE_BADALG = 21,
         DNS_RCODE_BADTRUNC = 22,
-        _DNS_RCODE_MAX_DEFINED
+        _DNS_RCODE_MAX_DEFINED,
+        _DNS_RCODE_MAX = 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
 };
 
 const char* dns_rcode_to_string(int i) _const_;
diff --git a/src/resolve/resolved-dns-server.c b/src/resolve/resolved-dns-server.c
index 5acfcb4239..bcbfa69aff 100644
--- a/src/resolve/resolved-dns-server.c
+++ b/src/resolve/resolved-dns-server.c
@@ -517,7 +517,7 @@ int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeature
         else
                 packet_size = server->received_udp_packet_max;
 
-        return dns_packet_append_opt(packet, packet_size, edns_do, NULL);
+        return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL);
 }
 
 int dns_server_ifindex(const DnsServer *s) {