resolved: add a DNS client stub resolver

Let's turn resolved into a something truly useful: a fully asynchronous
DNS stub resolver that subscribes to network changes.

(More to come: caching, LLMNR, mDNS/DNS-SD, DNSSEC, IDN, NSS module)

1 files changed, 132 insertions, 0 deletions

diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
new file mode 100644
index 0000000000..18ed4ba0d7
--- /dev/null
+++ b/src/resolve/resolved-dns-packet.h
@@ -0,0 +1,132 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+ ***/
+
+typedef struct DnsPacketHeader DnsPacketHeader;
+typedef struct DnsPacket DnsPacket;
+
+#include <inttypes.h>
+
+#include "macro.h"
+#include "sparse-endian.h"
+#include "hashmap.h"
+#include "resolved-dns-rr.h"
+
+struct DnsPacketHeader {
+        uint16_t id;
+        be16_t flags;
+        be16_t qdcount;
+        be16_t ancount;
+        be16_t nscount;
+        be16_t arcount;
+};
+
+#define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
+#define DNS_PACKET_SIZE_START 512
+
+struct DnsPacket {
+        int n_ref;
+        size_t size, allocated, rindex;
+        Hashmap *names; /* For name compression */
+        void *data;
+        int ifindex;
+};
+
+static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
+        if (_unlikely_(!p))
+                return NULL;
+
+        if (p->data)
+                return p->data;
+
+        return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
+}
+
+#define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
+
+int dns_packet_new(DnsPacket **p, size_t mtu);
+int dns_packet_new_query(DnsPacket **p, size_t mtu);
+
+DnsPacket *dns_packet_ref(DnsPacket *p);
+DnsPacket *dns_packet_unref(DnsPacket *p);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
+
+int dns_packet_validate(DnsPacket *p);
+int dns_packet_validate_reply(DnsPacket *p);
+
+int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
+int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
+int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
+int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start);
+int dns_packet_append_name(DnsPacket *p, const char *name, size_t *start);
+int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, size_t *start);
+
+int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
+int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
+int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
+int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
+int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
+int dns_packet_read_name(DnsPacket *p, char **ret, size_t *start);
+int dns_packet_read_key(DnsPacket *p, DnsResourceKey *ret, size_t *start);
+int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
+
+int dns_packet_skip_question(DnsPacket *p);
+
+#define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
+        (((uint16_t) !!qr << 15) |  \
+         ((uint16_t) (opcode & 15) << 11) | \
+         ((uint16_t) !!aa << 10) | \
+         ((uint16_t) !!tc << 9) | \
+         ((uint16_t) !!rd << 8) | \
+         ((uint16_t) !!ra << 7) | \
+         ((uint16_t) !!ad << 5) | \
+         ((uint16_t) !!cd << 4) | \
+         ((uint16_t) (rcode & 15)))
+
+#define DNS_PACKET_RCODE(p) (be16toh(DNS_PACKET_HEADER(p)->flags) & 15)
+
+enum {
+        DNS_RCODE_SUCCESS = 0,
+        DNS_RCODE_FORMERR = 1,
+        DNS_RCODE_SERVFAIL = 2,
+        DNS_RCODE_NXDOMAIN = 3,
+        DNS_RCODE_NOTIMP = 4,
+        DNS_RCODE_REFUSED = 5,
+        DNS_RCODE_YXDOMAIN = 6,
+        DNS_RCODE_YXRRSET = 7,
+        DNS_RCODE_NXRRSET = 8,
+        DNS_RCODE_NOTAUTH = 9,
+        DNS_RCODE_NOTZONE = 10,
+        DNS_RCODE_BADVERS = 16,
+        DNS_RCODE_BADSIG = 16, /* duplicate value! */
+        DNS_RCODE_BADKEY = 17,
+        DNS_RCODE_BADTIME = 18,
+        DNS_RCODE_BADMODE = 19,
+        DNS_RCODE_BADNAME = 20,
+        DNS_RCODE_BADALG = 21,
+        DNS_RCODE_BADTRUNC = 22,
+        _DNS_RCODE_MAX_DEFINED
+};
+
+const char* dns_rcode_to_string(int i) _const_;
+int dns_rcode_from_string(const char *s) _pure_;