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authorLennart Poettering <lennart@poettering.net>2014-07-16 00:26:02 +0200
committerLennart Poettering <lennart@poettering.net>2014-07-16 00:31:38 +0200
commit74b2466e14a1961bf3ac0e8a60cfaceec705bd59 (patch)
tree48e9e848b04562dc1f547ba7079fb3568e03f0fe /src/resolve/resolved-dns-packet.c
parent337ede5693cb8860ee86a2d71ffedec682abf6bc (diff)
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)
Diffstat (limited to 'src/resolve/resolved-dns-packet.c')
-rw-r--r--src/resolve/resolved-dns-packet.c734
1 files changed, 734 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
new file mode 100644
index 0000000000..2a666924b0
--- /dev/null
+++ b/src/resolve/resolved-dns-packet.c
@@ -0,0 +1,734 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ 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/>.
+ ***/
+
+#include "utf8.h"
+
+#include "resolved-dns-domain.h"
+#include "resolved-dns-packet.h"
+
+int dns_packet_new(DnsPacket **ret, size_t mtu) {
+ DnsPacket *p;
+ size_t a;
+
+ assert(ret);
+
+ if (mtu <= 0)
+ a = DNS_PACKET_SIZE_START;
+ else
+ a = mtu;
+
+ if (a < DNS_PACKET_HEADER_SIZE)
+ a = DNS_PACKET_HEADER_SIZE;
+
+ p = malloc0(ALIGN(sizeof(DnsPacket)) + a);
+ if (!p)
+ return -ENOMEM;
+
+ p->size = p->rindex = DNS_PACKET_HEADER_SIZE;
+ p->allocated = a;
+ p->n_ref = 1;
+
+ *ret = p;
+
+ return 0;
+}
+
+int dns_packet_new_query(DnsPacket **ret, size_t mtu) {
+ DnsPacket *p;
+ DnsPacketHeader *h;
+ int r;
+
+ assert(ret);
+
+ r = dns_packet_new(&p, mtu);
+ if (r < 0)
+ return r;
+
+ h = DNS_PACKET_HEADER(p);
+ h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0, 0, 0, 0, 1, 0, 0, 0, 0));
+
+ *ret = p;
+ return 0;
+}
+
+DnsPacket *dns_packet_ref(DnsPacket *p) {
+
+ if (!p)
+ return NULL;
+
+ assert(p->n_ref > 0);
+ p->n_ref++;
+ return p;
+}
+
+static void dns_packet_free(DnsPacket *p) {
+ char *s;
+
+ assert(p);
+
+ while ((s = hashmap_steal_first_key(p->names)))
+ free(s);
+ hashmap_free(p->names);
+
+ free(p->data);
+ free(p);
+}
+
+DnsPacket *dns_packet_unref(DnsPacket *p) {
+ if (!p)
+ return NULL;
+
+ assert(p->n_ref > 0);
+
+ if (p->n_ref == 1)
+ dns_packet_free(p);
+ else
+ p->n_ref--;
+
+ return NULL;
+}
+
+int dns_packet_validate(DnsPacket *p) {
+ assert(p);
+
+ if (p->size < DNS_PACKET_HEADER_SIZE)
+ return -EBADMSG;
+
+ return 0;
+}
+
+int dns_packet_validate_reply(DnsPacket *p) {
+ DnsPacketHeader *h;
+ int r;
+
+ assert(p);
+
+ r = dns_packet_validate(p);
+ if (r < 0)
+ return r;
+
+ h = DNS_PACKET_HEADER(p);
+
+ /* Check QR field */
+ if ((be16toh(h->flags) & 1) == 0)
+ return -EBADMSG;
+
+ /* Check opcode field */
+ if (((be16toh(h->flags) >> 1) & 15) != 0)
+ return -EBADMSG;
+
+ return 0;
+}
+
+static int dns_packet_extend(DnsPacket *p, size_t add, void **ret, size_t *start) {
+ assert(p);
+
+ if (p->size + add > p->allocated)
+ return -ENOMEM;
+
+ if (start)
+ *start = p->size;
+
+ if (ret)
+ *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->size;
+
+ p->size += add;
+ return 0;
+}
+
+static void dns_packet_truncate(DnsPacket *p, size_t sz) {
+ Iterator i;
+ char *s;
+ void *n;
+
+ assert(p);
+
+ if (p->size <= sz)
+ return;
+
+ HASHMAP_FOREACH_KEY(s, n, p->names, i) {
+
+ if (PTR_TO_SIZE(n) < sz)
+ continue;
+
+ hashmap_remove(p->names, s);
+ free(s);
+ }
+
+ p->size = sz;
+}
+
+int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start) {
+ void *d;
+ int r;
+
+ assert(p);
+
+ r = dns_packet_extend(p, sizeof(uint8_t), &d, start);
+ if (r < 0)
+ return r;
+
+ ((uint8_t*) d)[0] = v;
+
+ return 0;
+}
+
+int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start) {
+ void *d;
+ int r;
+
+ assert(p);
+
+ r = dns_packet_extend(p, sizeof(uint16_t), &d, start);
+ if (r < 0)
+ return r;
+
+ ((uint8_t*) d)[0] = (uint8_t) (v >> 8);
+ ((uint8_t*) d)[1] = (uint8_t) (v & 255);
+
+ return 0;
+}
+
+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;
+}
+
+int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, size_t *start) {
+ void *w;
+ int r;
+
+ assert(p);
+ assert(d);
+
+ if (l > DNS_LABEL_MAX)
+ return -E2BIG;
+
+ r = dns_packet_extend(p, 1 + l, &w, start);
+ if (r < 0)
+ return r;
+
+ ((uint8_t*) w)[0] = (uint8_t) l;
+ memcpy(((uint8_t*) w) + 1, d, l);
+
+ return 0;
+}
+
+int dns_packet_append_name(DnsPacket *p, const char *name, size_t *start) {
+ size_t saved_size;
+ int r;
+
+ assert(p);
+ assert(name);
+
+ saved_size = p->size;
+
+ while (*name) {
+ _cleanup_free_ char *s = NULL;
+ char label[DNS_LABEL_MAX];
+ size_t n;
+
+ n = PTR_TO_SIZE(hashmap_get(p->names, name));
+ if (n > 0) {
+ assert(n < p->size);
+
+ if (n < 0x4000) {
+ r = dns_packet_append_uint16(p, 0xC000 | n, NULL);
+ if (r < 0)
+ goto fail;
+
+ goto done;
+ }
+ }
+
+ s = strdup(name);
+ if (!s) {
+ r = -ENOMEM;
+ goto fail;
+ }
+
+ r = dns_label_unescape(&name, label, sizeof(label));
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_append_label(p, label, r, &n);
+ if (r < 0)
+ goto fail;
+
+ r = hashmap_ensure_allocated(&p->names, dns_name_hash_func, dns_name_compare_func);
+ if (r < 0)
+ goto fail;
+
+ r = hashmap_put(p->names, s, SIZE_TO_PTR(n));
+ if (r < 0)
+ goto fail;
+
+ s = NULL;
+ }
+
+ r = dns_packet_append_uint8(p, 0, NULL);
+ if (r < 0)
+ return r;
+
+done:
+ if (start)
+ *start = saved_size;
+
+ return 0;
+
+fail:
+ dns_packet_truncate(p, saved_size);
+ return r;
+}
+
+int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, size_t *start) {
+ size_t saved_size;
+ int r;
+
+ assert(p);
+ assert(k);
+
+ saved_size = p->size;
+
+ r = dns_packet_append_name(p, k->name, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_append_uint16(p, k->type, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_append_uint16(p, k->class, NULL);
+ if (r < 0)
+ goto fail;
+
+ if (start)
+ *start = saved_size;
+
+ return 0;
+
+fail:
+ dns_packet_truncate(p, saved_size);
+ return r;
+}
+
+int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
+ assert(p);
+
+ if (p->rindex + sz > p->size)
+ return -EMSGSIZE;
+
+ if (ret)
+ *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex;
+
+ if (start)
+ *start = p->rindex;
+
+ p->rindex += sz;
+ return 0;
+}
+
+static void dns_packet_rewind(DnsPacket *p, size_t idx) {
+ assert(p);
+ assert(idx <= p->size);
+ assert(idx >= DNS_PACKET_HEADER_SIZE);
+
+ p->rindex = idx;
+}
+
+int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) {
+ const void *d;
+ int r;
+
+ assert(p);
+
+ r = dns_packet_read(p, sizeof(uint8_t), &d, start);
+ if (r < 0)
+ return r;
+
+ *ret = ((uint8_t*) d)[0];
+ return 0;
+}
+
+int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) {
+ const void *d;
+ int r;
+
+ assert(p);
+
+ r = dns_packet_read(p, sizeof(uint16_t), &d, start);
+ if (r < 0)
+ return r;
+
+ *ret = (((uint16_t) ((uint8_t*) d)[0]) << 8) |
+ ((uint16_t) ((uint8_t*) d)[1]);
+ return 0;
+}
+
+int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) {
+ const void *d;
+ int r;
+
+ assert(p);
+
+ r = dns_packet_read(p, sizeof(uint32_t), &d, start);
+ if (r < 0)
+ return r;
+
+ *ret = (((uint32_t) ((uint8_t*) d)[0]) << 24) |
+ (((uint32_t) ((uint8_t*) d)[1]) << 16) |
+ (((uint32_t) ((uint8_t*) d)[2]) << 8) |
+ ((uint32_t) ((uint8_t*) d)[3]);
+
+ return 0;
+}
+
+int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) {
+ size_t saved_rindex;
+ const void *d;
+ char *t;
+ uint8_t c;
+ int r;
+
+ assert(p);
+
+ saved_rindex = p->rindex;
+
+ r = dns_packet_read_uint8(p, &c, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_read(p, c, &d, NULL);
+ if (r < 0)
+ goto fail;
+
+ if (memchr(d, 0, c)) {
+ r = -EBADMSG;
+ goto fail;
+ }
+
+ t = strndup(d, c);
+ if (!t) {
+ r = -ENOMEM;
+ goto fail;
+ }
+
+ if (!utf8_is_valid(t)) {
+ free(t);
+ r = -EBADMSG;
+ goto fail;
+ }
+
+ *ret = t;
+
+ if (start)
+ *start = saved_rindex;
+
+ return 0;
+
+fail:
+ dns_packet_rewind(p, saved_rindex);
+ return r;
+}
+
+int dns_packet_read_name(DnsPacket *p, char **_ret, size_t *start) {
+ size_t saved_rindex, after_rindex = 0;
+ _cleanup_free_ char *ret = NULL;
+ size_t n = 0, allocated = 0;
+ bool first = true;
+ int r;
+
+ assert(p);
+ assert(_ret);
+
+ saved_rindex = p->rindex;
+
+ for (;;) {
+ uint8_t c, d;
+
+ r = dns_packet_read_uint8(p, &c, NULL);
+ if (r < 0)
+ goto fail;
+
+ if (c == 0)
+ /* End of name */
+ break;
+ else if (c <= 63) {
+ _cleanup_free_ char *t = NULL;
+ const char *label;
+
+ /* Literal label */
+ r = dns_packet_read(p, c, (const void**) &label, NULL);
+ 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)) {
+ r = -ENOMEM;
+ goto fail;
+ }
+
+ if (!first)
+ ret[n++] = '.';
+ else
+ first = false;
+
+ memcpy(ret + n, t, c);
+ n += r;
+ continue;
+ } else if ((c & 0xc0) == 0xc0) {
+ uint16_t ptr;
+
+ /* Pointer */
+ r = dns_packet_read_uint8(p, &d, NULL);
+ if (r < 0)
+ goto fail;
+
+ ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
+ if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= saved_rindex) {
+ r = -EBADMSG;
+ goto fail;
+ }
+
+ if (after_rindex == 0)
+ after_rindex = p->rindex;
+
+ p->rindex = ptr;
+ } else
+ goto fail;
+ }
+
+ if (!GREEDY_REALLOC(ret, allocated, n + 1)) {
+ r = -ENOMEM;
+ goto fail;
+ }
+
+ ret[n] = 0;
+
+ if (after_rindex != 0)
+ p->rindex= after_rindex;
+
+ *_ret = ret;
+ ret = NULL;
+
+ if (start)
+ *start = saved_rindex;
+
+ return 0;
+
+fail:
+ dns_packet_rewind(p, saved_rindex);
+ return r;
+}
+
+int dns_packet_read_key(DnsPacket *p, DnsResourceKey *ret, size_t *start) {
+ _cleanup_(dns_resource_key_free) DnsResourceKey k = {};
+ size_t saved_rindex;
+ int r;
+
+ assert(p);
+ assert(ret);
+
+ saved_rindex = p->rindex;
+
+ r = dns_packet_read_name(p, &k.name, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_read_uint16(p, &k.type, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_read_uint16(p, &k.class, NULL);
+ if (r < 0)
+ goto fail;
+
+ *ret = k;
+ zero(k);
+
+ if (start)
+ *start = saved_rindex;
+
+ return 0;
+fail:
+ dns_packet_rewind(p, saved_rindex);
+ return r;
+}
+
+int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+ size_t saved_rindex, offset;
+ uint16_t rdlength;
+ const void *d;
+ int r;
+
+ assert(p);
+ assert(ret);
+
+ saved_rindex = p->rindex;
+
+ rr = dns_resource_record_new();
+ if (!rr)
+ goto fail;
+
+ r = dns_packet_read_key(p, &rr->key, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_read_uint32(p, &rr->ttl, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_read_uint16(p, &rdlength, NULL);
+ if (r < 0)
+ goto fail;
+
+ if (p->rindex + rdlength > p->size) {
+ r = -EBADMSG;
+ goto fail;
+ }
+
+ offset = p->rindex;
+
+ switch (rr->key.type) {
+
+ case DNS_TYPE_PTR:
+ case DNS_TYPE_NS:
+ case DNS_TYPE_CNAME:
+ r = dns_packet_read_name(p, &rr->ptr.name, NULL);
+ break;
+
+ case DNS_TYPE_HINFO:
+ r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = dns_packet_read_string(p, &rr->hinfo.os, NULL);
+ break;
+
+ case DNS_TYPE_A:
+ r = dns_packet_read(p, sizeof(struct in_addr), &d, NULL);
+ if (r < 0)
+ goto fail;
+
+ memcpy(&rr->a.in_addr, d, sizeof(struct in_addr));
+ break;
+
+ case DNS_TYPE_AAAA:
+ r = dns_packet_read(p, sizeof(struct in6_addr), &d, NULL);
+ if (r < 0)
+ goto fail;
+
+ memcpy(&rr->aaaa.in6_addr, d, sizeof(struct in6_addr));
+ break;
+
+ default:
+ r = dns_packet_read(p, rdlength, &d, NULL);
+ if (r < 0)
+ goto fail;
+
+ rr->generic.data = memdup(d, rdlength);
+ if (!rr->generic.data) {
+ r = -ENOMEM;
+ goto fail;
+ }
+
+ rr->generic.size = rdlength;
+ break;
+ }
+ if (r < 0)
+ goto fail;
+ if (p->rindex != offset + rdlength) {
+ r = -EBADMSG;
+ goto fail;
+ }
+
+ *ret = rr;
+ rr = NULL;
+
+ if (start)
+ *start = saved_rindex;
+
+ return 0;
+fail:
+ dns_packet_rewind(p, saved_rindex);
+ return r;
+}
+
+int dns_packet_skip_question(DnsPacket *p) {
+ int r;
+
+ unsigned i, n;
+ assert(p);
+
+ n = be16toh(DNS_PACKET_HEADER(p)->qdcount);
+ for (i = 0; i < n; i++) {
+ _cleanup_(dns_resource_key_free) DnsResourceKey key = {};
+
+ r = dns_packet_read_key(p, &key, NULL);
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
+
+static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
+ [DNS_RCODE_SUCCESS] = "SUCCESS",
+ [DNS_RCODE_FORMERR] = "FORMERR",
+ [DNS_RCODE_SERVFAIL] = "SERVFAIL",
+ [DNS_RCODE_NXDOMAIN] = "NXDOMAIN",
+ [DNS_RCODE_NOTIMP] = "NOTIMP",
+ [DNS_RCODE_REFUSED] = "REFUSED",
+ [DNS_RCODE_YXDOMAIN] = "YXDOMAIN",
+ [DNS_RCODE_YXRRSET] = "YRRSET",
+ [DNS_RCODE_NXRRSET] = "NXRRSET",
+ [DNS_RCODE_NOTAUTH] = "NOTAUTH",
+ [DNS_RCODE_NOTZONE] = "NOTZONE",
+ [DNS_RCODE_BADVERS] = "BADVERS",
+ [DNS_RCODE_BADKEY] = "BADKEY",
+ [DNS_RCODE_BADTIME] = "BADTIME",
+ [DNS_RCODE_BADMODE] = "BADMODE",
+ [DNS_RCODE_BADNAME] = "BADNAME",
+ [DNS_RCODE_BADALG] = "BADALG",
+ [DNS_RCODE_BADTRUNC] = "BADTRUNC",
+};
+DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int);