]> git.ipfire.org Git - thirdparty/systemd.git/blobdiff - src/resolve/resolved-dns-packet.c
udevd: initialize fds to -1 and close them before exiting
[thirdparty/systemd.git] / src / resolve / resolved-dns-packet.c
index 4b6b6afae8b6828ce71d273dd3a20024837b14aa..a8a8632491908108183a1ce7df53ec1960c3b984 100644 (file)
@@ -28,6 +28,8 @@
 #include "utf8.h"
 #include "util.h"
 
+#define EDNS0_OPT_DO (1<<15)
+
 int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
         DnsPacket *p;
         size_t a;
@@ -56,6 +58,7 @@ int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
         p->size = p->rindex = DNS_PACKET_HEADER_SIZE;
         p->allocated = a;
         p->protocol = protocol;
+        p->opt_start = p->opt_size = (size_t) -1;
         p->n_ref = 1;
 
         *ret = p;
@@ -63,20 +66,18 @@ int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
         return 0;
 }
 
-int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
-        DnsPacket *p;
-        DnsPacketHeader *h;
-        int r;
+void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated) {
 
-        assert(ret);
+        DnsPacketHeader *h;
 
-        r = dns_packet_new(&p, protocol, mtu);
-        if (r < 0)
-                return r;
+        assert(p);
 
         h = DNS_PACKET_HEADER(p);
 
-        if (protocol == DNS_PROTOCOL_LLMNR)
+        switch(p->protocol) {
+        case DNS_PROTOCOL_LLMNR:
+                assert(!truncated);
+
                 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
                                                          0 /* opcode */,
                                                          0 /* c */,
@@ -86,7 +87,23 @@ int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
                                                          0 /* ad */,
                                                          0 /* cd */,
                                                          0 /* rcode */));
-        else
+                break;
+
+        case DNS_PROTOCOL_MDNS:
+                h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0         /* qr */,
+                                                         0         /* opcode */,
+                                                         0         /* aa */,
+                                                         truncated /* tc */,
+                                                         0         /* rd (ask for recursion) */,
+                                                         0         /* ra */,
+                                                         0         /* ad */,
+                                                         0         /* cd */,
+                                                         0         /* rcode */));
+                break;
+
+        default:
+                assert(!truncated);
+
                 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
                                                          0 /* opcode */,
                                                          0 /* aa */,
@@ -94,8 +111,25 @@ int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
                                                          1 /* rd (ask for recursion) */,
                                                          0 /* ra */,
                                                          0 /* ad */,
-                                                         0 /* cd */,
+                                                         dnssec_checking_disabled /* cd */,
                                                          0 /* rcode */));
+        }
+}
+
+int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled) {
+        DnsPacket *p;
+        int r;
+
+        assert(ret);
+
+        r = dns_packet_new(&p, protocol, mtu);
+        if (r < 0)
+                return r;
+
+        /* Always set the TC bit to 0 initially.
+         * If there are multiple packets later, we'll update the bit shortly before sending.
+         */
+        dns_packet_set_flags(p, dnssec_checking_disabled, false);
 
         *ret = p;
         return 0;
@@ -106,6 +140,8 @@ DnsPacket *dns_packet_ref(DnsPacket *p) {
         if (!p)
                 return NULL;
 
+        assert(!p->on_stack);
+
         assert(p->n_ref > 0);
         p->n_ref++;
         return p;
@@ -118,13 +154,16 @@ static void dns_packet_free(DnsPacket *p) {
 
         dns_question_unref(p->question);
         dns_answer_unref(p->answer);
+        dns_resource_record_unref(p->opt);
 
         while ((s = hashmap_steal_first_key(p->names)))
                 free(s);
         hashmap_free(p->names);
 
         free(p->_data);
-        free(p);
+
+        if (!p->on_stack)
+                free(p);
 }
 
 DnsPacket *dns_packet_unref(DnsPacket *p) {
@@ -133,6 +172,8 @@ DnsPacket *dns_packet_unref(DnsPacket *p) {
 
         assert(p->n_ref > 0);
 
+        dns_packet_unref(p->more);
+
         if (p->n_ref == 1)
                 dns_packet_free(p);
         else
@@ -169,6 +210,7 @@ int dns_packet_validate_reply(DnsPacket *p) {
                 return -EBADMSG;
 
         switch (p->protocol) {
+
         case DNS_PROTOCOL_LLMNR:
                 /* RFC 4795, Section 2.1.1. says to discard all replies with QDCOUNT != 1 */
                 if (DNS_PACKET_QDCOUNT(p) != 1)
@@ -176,6 +218,13 @@ int dns_packet_validate_reply(DnsPacket *p) {
 
                 break;
 
+        case DNS_PROTOCOL_MDNS:
+                /* RFC 6762, Section 18 */
+                if (DNS_PACKET_RCODE(p) != 0)
+                        return -EBADMSG;
+
+                break;
+
         default:
                 break;
         }
@@ -202,6 +251,7 @@ int dns_packet_validate_query(DnsPacket *p) {
                 return -EBADMSG;
 
         switch (p->protocol) {
+
         case DNS_PROTOCOL_LLMNR:
                 /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
                 if (DNS_PACKET_QDCOUNT(p) != 1)
@@ -217,6 +267,18 @@ int dns_packet_validate_query(DnsPacket *p) {
 
                 break;
 
+        case DNS_PROTOCOL_MDNS:
+                /* RFC 6762, Section 18 */
+                if (DNS_PACKET_AA(p)    != 0 ||
+                    DNS_PACKET_RD(p)    != 0 ||
+                    DNS_PACKET_RA(p)    != 0 ||
+                    DNS_PACKET_AD(p)    != 0 ||
+                    DNS_PACKET_CD(p)    != 0 ||
+                    DNS_PACKET_RCODE(p) != 0)
+                        return -EBADMSG;
+
+                break;
+
         default:
                 break;
         }
@@ -267,7 +329,7 @@ static int dns_packet_extend(DnsPacket *p, size_t add, void **ret, size_t *start
         return 0;
 }
 
-static void dns_packet_truncate(DnsPacket *p, size_t sz) {
+void dns_packet_truncate(DnsPacket *p, size_t sz) {
         Iterator i;
         char *s;
         void *n;
@@ -349,25 +411,10 @@ int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start) {
 }
 
 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start) {
-        void *d;
-        size_t l;
-        int r;
-
         assert(p);
         assert(s);
 
-        l = strlen(s);
-        if (l > 255)
-                return -E2BIG;
-
-        r = dns_packet_extend(p, 1 + l, &d, start);
-        if (r < 0)
-                return r;
-
-        ((uint8_t*) d)[0] = (uint8_t) l;
-        memcpy(((uint8_t*) d) + 1, s, l);
-
-        return 0;
+        return dns_packet_append_raw_string(p, s, strlen(s), start);
 }
 
 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start) {
@@ -392,22 +439,40 @@ int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_
         return 0;
 }
 
-int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, size_t *start) {
-        void *w;
+int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, bool canonical_candidate, size_t *start) {
+        uint8_t *w;
         int r;
 
+        /* Append a label to a packet. Optionally, does this in DNSSEC
+         * canonical form, if this label is marked as a candidate for
+         * it, and the canonical form logic is enabled for the
+         * packet */
+
         assert(p);
         assert(d);
 
         if (l > DNS_LABEL_MAX)
                 return -E2BIG;
 
-        r = dns_packet_extend(p, 1 + l, &w, start);
+        r = dns_packet_extend(p, 1 + l, (void**) &w, start);
         if (r < 0)
                 return r;
 
-        ((uint8_t*) w)[0] = (uint8_t) l;
-        memcpy(((uint8_t*) w) + 1, d, l);
+        *(w++) = (uint8_t) l;
+
+        if (p->canonical_form && canonical_candidate) {
+                size_t i;
+
+                /* Generate in canonical form, as defined by DNSSEC
+                 * RFC 4034, Section 6.2, i.e. all lower-case. */
+
+                for (i = 0; i < l; i++)
+                        w[i] = (uint8_t) ascii_tolower(d[i]);
+        } else
+                /* Otherwise, just copy the string unaltered. This is
+                 * essential for DNS-SD, where the casing of labels
+                 * matters and needs to be retained. */
+                memcpy(w, d, l);
 
         return 0;
 }
@@ -416,6 +481,7 @@ int dns_packet_append_name(
                 DnsPacket *p,
                 const char *name,
                 bool allow_compression,
+                bool canonical_candidate,
                 size_t *start) {
 
         size_t saved_size;
@@ -429,8 +495,8 @@ int dns_packet_append_name(
 
         saved_size = p->size;
 
-        while (*name) {
-                _cleanup_free_ char *s = NULL;
+        while (!dns_name_is_root(name)) {
+                const char *z = name;
                 char label[DNS_LABEL_MAX];
                 size_t n = 0;
                 int k;
@@ -449,12 +515,6 @@ int dns_packet_append_name(
                         }
                 }
 
-                s = strdup(name);
-                if (!s) {
-                        r = -ENOMEM;
-                        goto fail;
-                }
-
                 r = dns_label_unescape(&name, label, sizeof(label));
                 if (r < 0)
                         goto fail;
@@ -470,11 +530,19 @@ int dns_packet_append_name(
                 if (k > 0)
                         r = k;
 
-                r = dns_packet_append_label(p, label, r, &n);
+                r = dns_packet_append_label(p, label, r, canonical_candidate, &n);
                 if (r < 0)
                         goto fail;
 
                 if (allow_compression) {
+                        _cleanup_free_ char *s = NULL;
+
+                        s = strdup(z);
+                        if (!s) {
+                                r = -ENOMEM;
+                                goto fail;
+                        }
+
                         r = hashmap_ensure_allocated(&p->names, &dns_name_hash_ops);
                         if (r < 0)
                                 goto fail;
@@ -511,7 +579,7 @@ int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, size_t *start)
 
         saved_size = p->size;
 
-        r = dns_packet_append_name(p, DNS_RESOURCE_KEY_NAME(k), true, NULL);
+        r = dns_packet_append_name(p, DNS_RESOURCE_KEY_NAME(k), true, true, NULL);
         if (r < 0)
                 goto fail;
 
@@ -533,7 +601,7 @@ fail:
         return r;
 }
 
-static int dns_packet_append_type_window(DnsPacket *p, uint8_t window, uint8_t length, uint8_t *types, size_t *start) {
+static int dns_packet_append_type_window(DnsPacket *p, uint8_t window, uint8_t length, const uint8_t *types, size_t *start) {
         size_t saved_size;
         int r;
 
@@ -574,7 +642,6 @@ static int dns_packet_append_types(DnsPacket *p, Bitmap *types, size_t *start) {
         int r;
 
         assert(p);
-        assert(types);
 
         saved_size = p->size;
 
@@ -590,27 +657,143 @@ static int dns_packet_append_types(DnsPacket *p, Bitmap *types, size_t *start) {
                 }
 
                 window = n >> 8;
-
                 entry = n & 255;
 
                 bitmaps[entry / 8] |= 1 << (7 - (entry % 8));
         }
 
-        r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL);
+        if (bitmaps[entry / 8] != 0) {
+                r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL);
+                if (r < 0)
+                        goto fail;
+        }
+
+        if (start)
+                *start = saved_size;
+
+        return 0;
+fail:
+        dns_packet_truncate(p, saved_size);
+        return r;
+}
+
+/* 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) {
+        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);
+
+        if (p->opt_start != (size_t) -1)
+                return -EBUSY;
+
+        assert(p->opt_size == (size_t) -1);
+
+        saved_size = p->size;
+
+        /* empty name */
+        r = dns_packet_append_uint8(p, 0, NULL);
+        if (r < 0)
+                return r;
+
+        /* type */
+        r = dns_packet_append_uint16(p, DNS_TYPE_OPT, NULL);
+        if (r < 0)
+                goto fail;
+
+        /* 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);
+        if (r < 0)
+                goto fail;
+
+        /* flags: DNSSEC OK (DO), see RFC3225 */
+        r = dns_packet_append_uint16(p, edns0_do ? EDNS0_OPT_DO : 0, NULL);
+        if (r < 0)
+                goto fail;
+
+        /* RDLENGTH */
+
+        if (edns0_do) {
+                /* If DO is on, also append RFC6975 Algorithm data */
+
+                static const uint8_t rfc6975[] = {
+
+                        0, 5, /* OPTION_CODE: DAU */
+                        0, 6, /* LIST_LENGTH */
+                        DNSSEC_ALGORITHM_RSASHA1,
+                        DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
+                        DNSSEC_ALGORITHM_RSASHA256,
+                        DNSSEC_ALGORITHM_RSASHA512,
+                        DNSSEC_ALGORITHM_ECDSAP256SHA256,
+                        DNSSEC_ALGORITHM_ECDSAP384SHA384,
+
+                        0, 6, /* OPTION_CODE: DHU */
+                        0, 3, /* LIST_LENGTH */
+                        DNSSEC_DIGEST_SHA1,
+                        DNSSEC_DIGEST_SHA256,
+                        DNSSEC_DIGEST_SHA384,
+
+                        0, 7, /* OPTION_CODE: N3U */
+                        0, 1, /* LIST_LENGTH */
+                        NSEC3_ALGORITHM_SHA1,
+                };
+
+                r = dns_packet_append_uint16(p, sizeof(rfc6975), NULL);
+                if (r < 0)
+                        goto fail;
+
+                r = dns_packet_append_blob(p, rfc6975, sizeof(rfc6975), NULL);
+        } else
+                r = dns_packet_append_uint16(p, 0, NULL);
+
         if (r < 0)
                 goto fail;
 
+        DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) + 1);
+
+        p->opt_start = saved_size;
+        p->opt_size = p->size - saved_size;
+
         if (start)
                 *start = saved_size;
 
         return 0;
+
 fail:
         dns_packet_truncate(p, saved_size);
         return r;
 }
 
-int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start) {
-        size_t saved_size, rdlength_offset, end, rdlength;
+int dns_packet_truncate_opt(DnsPacket *p) {
+        assert(p);
+
+        if (p->opt_start == (size_t) -1) {
+                assert(p->opt_size == (size_t) -1);
+                return 0;
+        }
+
+        assert(p->opt_size != (size_t) -1);
+        assert(DNS_PACKET_ARCOUNT(p) > 0);
+
+        if (p->opt_start + p->opt_size != p->size)
+                return -EBUSY;
+
+        dns_packet_truncate(p, p->opt_start);
+        DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) - 1);
+        p->opt_start = p->opt_size = (size_t) -1;
+
+        return 1;
+}
+
+int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start) {
+        size_t saved_size, rdlength_offset, end, rdlength, rds;
         int r;
 
         assert(p);
@@ -631,6 +814,8 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
         if (r < 0)
                 goto fail;
 
+        rds = p->size - saved_size;
+
         switch (rr->unparseable ? _DNS_TYPE_INVALID : rr->key->type) {
 
         case DNS_TYPE_SRV:
@@ -646,14 +831,14 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                 if (r < 0)
                         goto fail;
 
-                r = dns_packet_append_name(p, rr->srv.name, true, NULL);
+                r = dns_packet_append_name(p, rr->srv.name, true, false, NULL);
                 break;
 
         case DNS_TYPE_PTR:
         case DNS_TYPE_NS:
         case DNS_TYPE_CNAME:
         case DNS_TYPE_DNAME:
-                r = dns_packet_append_name(p, rr->ptr.name, true, NULL);
+                r = dns_packet_append_name(p, rr->ptr.name, true, false, NULL);
                 break;
 
         case DNS_TYPE_HINFO:
@@ -696,11 +881,11 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                 break;
 
         case DNS_TYPE_SOA:
-                r = dns_packet_append_name(p, rr->soa.mname, true, NULL);
+                r = dns_packet_append_name(p, rr->soa.mname, true, false, NULL);
                 if (r < 0)
                         goto fail;
 
-                r = dns_packet_append_name(p, rr->soa.rname, true, NULL);
+                r = dns_packet_append_name(p, rr->soa.rname, true, false, NULL);
                 if (r < 0)
                         goto fail;
 
@@ -728,7 +913,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                 if (r < 0)
                         goto fail;
 
-                r = dns_packet_append_name(p, rr->mx.exchange, true, NULL);
+                r = dns_packet_append_name(p, rr->mx.exchange, true, false, NULL);
                 break;
 
         case DNS_TYPE_LOC:
@@ -788,11 +973,11 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                 break;
 
         case DNS_TYPE_DNSKEY:
-                r = dns_packet_append_uint16(p, dnskey_to_flags(rr), NULL);
+                r = dns_packet_append_uint16(p, rr->dnskey.flags, NULL);
                 if (r < 0)
                         goto fail;
 
-                r = dns_packet_append_uint8(p, 3u, NULL);
+                r = dns_packet_append_uint8(p, rr->dnskey.protocol, NULL);
                 if (r < 0)
                         goto fail;
 
@@ -832,7 +1017,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                 if (r < 0)
                         goto fail;
 
-                r = dns_packet_append_name(p, rr->rrsig.signer, false, NULL);
+                r = dns_packet_append_name(p, rr->rrsig.signer, false, true, NULL);
                 if (r < 0)
                         goto fail;
 
@@ -840,7 +1025,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                 break;
 
         case DNS_TYPE_NSEC:
-                r = dns_packet_append_name(p, rr->nsec.next_domain_name, false, NULL);
+                r = dns_packet_append_name(p, rr->nsec.next_domain_name, false, false, NULL);
                 if (r < 0)
                         goto fail;
 
@@ -849,6 +1034,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                         goto fail;
 
                 break;
+
         case DNS_TYPE_NSEC3:
                 r = dns_packet_append_uint8(p, rr->nsec3.algorithm, NULL);
                 if (r < 0)
@@ -883,6 +1069,8 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
                         goto fail;
 
                 break;
+
+        case DNS_TYPE_OPT:
         case _DNS_TYPE_INVALID: /* unparseable */
         default:
 
@@ -909,6 +1097,9 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
         if (start)
                 *start = saved_size;
 
+        if (rdata_start)
+                *rdata_start = rds;
+
         return 0;
 
 fail:
@@ -916,7 +1107,6 @@ fail:
         return r;
 }
 
-
 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
         assert(p);
 
@@ -1145,7 +1335,6 @@ int dns_packet_read_name(
                         /* End of name */
                         break;
                 else if (c <= 63) {
-                        _cleanup_free_ char *t = NULL;
                         const char *label;
 
                         /* Literal label */
@@ -1153,21 +1342,20 @@ int dns_packet_read_name(
                         if (r < 0)
                                 goto fail;
 
-                        r = dns_label_escape(label, c, &t);
-                        if (r < 0)
-                                goto fail;
-
-                        if (!GREEDY_REALLOC(ret, allocated, n + !first + strlen(t) + 1)) {
+                        if (!GREEDY_REALLOC(ret, allocated, n + !first + DNS_LABEL_ESCAPED_MAX)) {
                                 r = -ENOMEM;
                                 goto fail;
                         }
 
-                        if (!first)
-                                ret[n++] = '.';
-                        else
+                        if (first)
                                 first = false;
+                        else
+                                ret[n++] = '.';
+
+                        r = dns_label_escape(label, c, ret + n, DNS_LABEL_ESCAPED_MAX);
+                        if (r < 0)
+                                goto fail;
 
-                        memcpy(ret + n, t, r);
                         n += r;
                         continue;
                 } else if (allow_compression && (c & 0xc0) == 0xc0) {
@@ -1328,8 +1516,9 @@ fail:
         return r;
 }
 
-int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
+int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start) {
         _cleanup_free_ char *name = NULL;
+        bool cache_flush = false;
         uint16_t class, type;
         DnsResourceKey *key;
         size_t saved_rindex;
@@ -1352,6 +1541,15 @@ int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
         if (r < 0)
                 goto fail;
 
+        if (p->protocol == DNS_PROTOCOL_MDNS) {
+                /* See RFC6762, Section 10.2 */
+
+                if (type != DNS_TYPE_OPT && (class & MDNS_RR_CACHE_FLUSH)) {
+                        class &= ~MDNS_RR_CACHE_FLUSH;
+                        cache_flush = true;
+                }
+        }
+
         key = dns_resource_key_new_consume(class, type, name);
         if (!key) {
                 r = -ENOMEM;
@@ -1361,6 +1559,8 @@ int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
         name = NULL;
         *ret = key;
 
+        if (ret_cache_flush)
+                *ret_cache_flush = cache_flush;
         if (start)
                 *start = saved_rindex;
 
@@ -1376,22 +1576,12 @@ static bool loc_size_ok(uint8_t size) {
         return m <= 9 && e <= 9 && (m > 0 || e == 0);
 }
 
-static int dnskey_parse_flags(DnsResourceRecord *rr, uint16_t flags) {
-        assert(rr);
-
-        if (flags & ~(DNSKEY_FLAG_SEP | DNSKEY_FLAG_ZONE_KEY))
-                return -EBADMSG;
-
-        rr->dnskey.zone_key_flag = flags & DNSKEY_FLAG_ZONE_KEY;
-        rr->dnskey.sep_flag = flags & DNSKEY_FLAG_SEP;
-        return 0;
-}
-
-int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
+int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start) {
         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
         size_t saved_rindex, offset;
         uint16_t rdlength;
+        bool cache_flush;
         int r;
 
         assert(p);
@@ -1399,12 +1589,12 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 
         saved_rindex = p->rindex;
 
-        r = dns_packet_read_key(p, &key, NULL);
+        r = dns_packet_read_key(p, &key, &cache_flush, NULL);
         if (r < 0)
                 goto fail;
 
-        if (key->class == DNS_CLASS_ANY ||
-            key->type == DNS_TYPE_ANY) {
+        if (!dns_class_is_valid_rr(key->class)||
+            !dns_type_is_valid_rr(key->type)) {
                 r = -EBADMSG;
                 goto fail;
         }
@@ -1419,6 +1609,11 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
         if (r < 0)
                 goto fail;
 
+        /* RFC 2181, Section 8, suggests to
+         * treat a TTL with the MSB set as a zero TTL. */
+        if (rr->ttl & UINT32_C(0x80000000))
+                rr->ttl = 0;
+
         r = dns_packet_read_uint16(p, &rdlength, NULL);
         if (r < 0)
                 goto fail;
@@ -1629,6 +1824,7 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
                 }
 
                 break;
+
         case DNS_TYPE_SSHFP:
                 r = dns_packet_read_uint8(p, &rr->sshfp.algorithm, NULL);
                 if (r < 0)
@@ -1651,28 +1847,15 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 
                 break;
 
-        case DNS_TYPE_DNSKEY: {
-                uint16_t flags;
-                uint8_t proto;
-
-                r = dns_packet_read_uint16(p, &flags, NULL);
-                if (r < 0)
-                        goto fail;
-
-                r = dnskey_parse_flags(rr, flags);
+        case DNS_TYPE_DNSKEY:
+                r = dns_packet_read_uint16(p, &rr->dnskey.flags, NULL);
                 if (r < 0)
                         goto fail;
 
-                r = dns_packet_read_uint8(p, &proto, NULL);
+                r = dns_packet_read_uint8(p, &rr->dnskey.protocol, NULL);
                 if (r < 0)
                         goto fail;
 
-                /* protocol is required to be always 3 */
-                if (proto != 3) {
-                        r = -EBADMSG;
-                        goto fail;
-                }
-
                 r = dns_packet_read_uint8(p, &rr->dnskey.algorithm, NULL);
                 if (r < 0)
                         goto fail;
@@ -1689,7 +1872,6 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
                 }
 
                 break;
-        }
 
         case DNS_TYPE_RRSIG:
                 r = dns_packet_read_uint16(p, &rr->rrsig.type_covered, NULL);
@@ -1737,8 +1919,16 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 
                 break;
 
-        case DNS_TYPE_NSEC:
-                r = dns_packet_read_name(p, &rr->nsec.next_domain_name, false, NULL);
+        case DNS_TYPE_NSEC: {
+
+                /*
+                 * RFC6762, section 18.14 explictly states mDNS should use name compression.
+                 * This contradicts RFC3845, section 2.1.1
+                 */
+
+                bool allow_compressed = p->protocol == DNS_PROTOCOL_MDNS;
+
+                r = dns_packet_read_name(p, &rr->nsec.next_domain_name, allow_compressed, NULL);
                 if (r < 0)
                         goto fail;
 
@@ -1751,7 +1941,7 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
                  * without the NSEC bit set. */
 
                 break;
-
+        }
         case DNS_TYPE_NSEC3: {
                 uint8_t size;
 
@@ -1797,6 +1987,8 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 
                 break;
         }
+
+        case DNS_TYPE_OPT: /* we only care about the header of OPT for now. */
         default:
         unparseable:
                 r = dns_packet_read_memdup(p, rdlength, &rr->generic.data, &rr->generic.size, NULL);
@@ -1814,6 +2006,8 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
         *ret = rr;
         rr = NULL;
 
+        if (ret_cache_flush)
+                *ret_cache_flush = cache_flush;
         if (start)
                 *start = saved_rindex;
 
@@ -1846,11 +2040,22 @@ int dns_packet_extract(DnsPacket *p) {
 
                 for (i = 0; i < n; i++) {
                         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
+                        bool cache_flush;
 
-                        r = dns_packet_read_key(p, &key, NULL);
+                        r = dns_packet_read_key(p, &key, &cache_flush, NULL);
                         if (r < 0)
                                 goto finish;
 
+                        if (cache_flush) {
+                                r = -EBADMSG;
+                                goto finish;
+                        }
+
+                        if (!dns_type_is_valid_query(key->type)) {
+                                r = -EBADMSG;
+                                goto finish;
+                        }
+
                         r = dns_question_add(question, key);
                         if (r < 0)
                                 goto finish;
@@ -1867,14 +2072,49 @@ int dns_packet_extract(DnsPacket *p) {
 
                 for (i = 0; i < n; i++) {
                         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+                        bool cache_flush;
 
-                        r = dns_packet_read_rr(p, &rr, NULL);
+                        r = dns_packet_read_rr(p, &rr, &cache_flush, NULL);
                         if (r < 0)
                                 goto finish;
 
-                        r = dns_answer_add(answer, rr, p->ifindex);
-                        if (r < 0)
-                                goto finish;
+                        if (rr->key->type == DNS_TYPE_OPT) {
+
+                                if (!dns_name_is_root(DNS_RESOURCE_KEY_NAME(rr->key))) {
+                                        r = -EBADMSG;
+                                        goto finish;
+                                }
+
+                                /* Note that we accept the OPT RR in
+                                 * any section, not just in the
+                                 * additional section, as some routers
+                                 * (Belkin!)  blindly copy the OPT RR
+                                 * from the query to the reply packet,
+                                 * and don't get the section right. */
+
+                                /* Two OPT RRs? */
+                                if (p->opt) {
+                                        r = -EBADMSG;
+                                        goto finish;
+                                }
+
+                                p->opt = dns_resource_record_ref(rr);
+                        } else {
+
+                                /* According to RFC 4795, section
+                                 * 2.9. only the RRs from the Answer
+                                 * section shall be cached. Hence mark
+                                 * only those RRs as cacheable by
+                                 * default, but not the ones from the
+                                 * Additional or Authority
+                                 * sections. */
+
+                                r = dns_answer_add(answer, rr, p->ifindex,
+                                                   (i < DNS_PACKET_ANCOUNT(p) ? DNS_ANSWER_CACHEABLE : 0) |
+                                                   (p->protocol == DNS_PROTOCOL_MDNS && !cache_flush ? DNS_ANSWER_SHARED_OWNER : 0));
+                                if (r < 0)
+                                        goto finish;
+                        }
                 }
         }
 
@@ -1893,6 +2133,30 @@ finish:
         return r;
 }
 
+int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key) {
+        int r;
+
+        assert(p);
+        assert(key);
+
+        /* Checks if the specified packet is a reply for the specified
+         * key and the specified key is the only one in the question
+         * section. */
+
+        if (DNS_PACKET_QR(p) != 1)
+                return 0;
+
+        /* Let's unpack the packet, if that hasn't happened yet. */
+        r = dns_packet_extract(p);
+        if (r < 0)
+                return r;
+
+        if (p->question->n_keys != 1)
+                return 0;
+
+        return dns_resource_key_equal(p->question->keys[0], key);
+}
+
 static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
         [DNS_RCODE_SUCCESS] = "SUCCESS",
         [DNS_RCODE_FORMERR] = "FORMERR",
@@ -1921,17 +2185,3 @@ static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = {
         [DNS_PROTOCOL_LLMNR] = "llmnr",
 };
 DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol);
-
-static const char* const dnssec_algorithm_table[_DNSSEC_ALGORITHM_MAX_DEFINED] = {
-        [DNSSEC_ALGORITHM_RSAMD5]             = "RSAMD5",
-        [DNSSEC_ALGORITHM_DH]                 = "DH",
-        [DNSSEC_ALGORITHM_DSA]                = "DSA",
-        [DNSSEC_ALGORITHM_ECC]                = "ECC",
-        [DNSSEC_ALGORITHM_RSASHA1]            = "RSASHA1",
-        [DNSSEC_ALGORITHM_DSA_NSEC3_SHA1]     = "DSA-NSEC3-SHA1",
-        [DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1] = "RSASHA1-NSEC3-SHA1",
-        [DNSSEC_ALGORITHM_INDIRECT]           = "INDIRECT",
-        [DNSSEC_ALGORITHM_PRIVATEDNS]         = "PRIVATEDNS",
-        [DNSSEC_ALGORITHM_PRIVATEOID]         = "PRIVATEOID",
-};
-DEFINE_STRING_TABLE_LOOKUP(dnssec_algorithm, int);