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systemd/src/resolve/resolved-dns-answer.c
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <stdio.h>
#include "alloc-util.h"
#include "dns-domain.h"
#include "random-util.h"
#include "resolved-dns-answer.h"
#include "resolved-dns-dnssec.h"
#include "string-util.h"
static void dns_answer_item_hash_func(const DnsAnswerItem *a, struct siphash *state) {
assert(a);
assert(state);
siphash24_compress(&a->ifindex, sizeof(a->ifindex), state);
dns_resource_record_hash_func(a->rr, state);
}
static int dns_answer_item_compare_func(const DnsAnswerItem *a, const DnsAnswerItem *b) {
int r;
assert(a);
assert(b);
r = CMP(a->ifindex, b->ifindex);
if (r != 0)
return r;
return dns_resource_record_compare_func(a->rr, b->rr);
}
DEFINE_PRIVATE_HASH_OPS(dns_answer_item_hash_ops, DnsAnswerItem, dns_answer_item_hash_func, dns_answer_item_compare_func);
DnsAnswer *dns_answer_new(size_t n) {
_cleanup_set_free_ Set *s = NULL;
DnsAnswer *a;
if (n > UINT16_MAX) /* We can only place 64K RRs in an answer at max */
n = UINT16_MAX;
s = set_new(&dns_answer_item_hash_ops);
if (!s)
return NULL;
/* Higher multipliers give slightly higher efficiency through hash collisions, but the gains
* quickly drop off after 2. */
if (set_reserve(s, n * 2) < 0)
return NULL;
a = malloc0(offsetof(DnsAnswer, items) + sizeof(DnsAnswerItem) * n);
if (!a)
return NULL;
a->n_ref = 1;
a->n_allocated = n;
a->set_items = TAKE_PTR(s);
return a;
}
static void dns_answer_flush(DnsAnswer *a) {
DnsAnswerItem *item;
if (!a)
return;
a->set_items = set_free(a->set_items);
DNS_ANSWER_FOREACH_ITEM(item, a) {
dns_resource_record_unref(item->rr);
dns_resource_record_unref(item->rrsig);
}
a->n_rrs = 0;
}
static DnsAnswer *dns_answer_free(DnsAnswer *a) {
assert(a);
dns_answer_flush(a);
return mfree(a);
}
DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsAnswer, dns_answer, dns_answer_free);
static int dns_answer_add_raw(
DnsAnswer *a,
DnsResourceRecord *rr,
int ifindex,
DnsAnswerFlags flags,
DnsResourceRecord *rrsig) {
int r;
assert(rr);
if (!a)
return -ENOSPC;
if (a->n_rrs >= a->n_allocated)
return -ENOSPC;
a->items[a->n_rrs] = (DnsAnswerItem) {
.rr = rr,
.ifindex = ifindex,
.flags = flags,
.rrsig = dns_resource_record_ref(rrsig),
};
r = set_put(a->set_items, &a->items[a->n_rrs]);
if (r < 0)
return r;
if (r == 0)
return -EEXIST;
dns_resource_record_ref(rr);
a->n_rrs++;
return 1;
}
static int dns_answer_add_raw_all(DnsAnswer *a, DnsAnswer *source) {
DnsAnswerItem *item;
int r;
DNS_ANSWER_FOREACH_ITEM(item, source) {
r = dns_answer_add_raw(
a,
item->rr,
item->ifindex,
item->flags,
item->rrsig);
if (r < 0)
return r;
}
return 0;
}
int dns_answer_add(
DnsAnswer *a,
DnsResourceRecord *rr,
int ifindex,
DnsAnswerFlags flags,
DnsResourceRecord *rrsig) {
DnsAnswerItem tmp, *exist;
assert(rr);
if (!a)
return -ENOSPC;
if (a->n_ref > 1)
return -EBUSY;
tmp = (DnsAnswerItem) {
.rr = rr,
.ifindex = ifindex,
};
exist = set_get(a->set_items, &tmp);
if (exist) {
/* There's already an RR of the same RRset in place! Let's see if the TTLs more or less
* match. We don't really care if they match precisely, but we do care whether one is 0 and
* the other is not. See RFC 2181, Section 5.2. */
if ((rr->ttl == 0) != (exist->rr->ttl == 0))
return -EINVAL;
/* Entry already exists, keep the entry with the higher TTL. */
if (rr->ttl > exist->rr->ttl) {
dns_resource_record_unref(exist->rr);
exist->rr = dns_resource_record_ref(rr); /* lgtm [cpp/inconsistent-null-check] */
/* Update RRSIG and RR at the same time */
if (rrsig) {
dns_resource_record_ref(rrsig);
dns_resource_record_unref(exist->rrsig);
exist->rrsig = rrsig;
}
}
exist->flags |= flags;
return 0;
}
return dns_answer_add_raw(a, rr, ifindex, flags, rrsig);
}
static int dns_answer_add_all(DnsAnswer *a, DnsAnswer *b) {
DnsAnswerItem *item;
int r;
DNS_ANSWER_FOREACH_ITEM(item, b) {
r = dns_answer_add(a, item->rr, item->ifindex, item->flags, item->rrsig);
if (r < 0)
return r;
}
return 0;
}
int dns_answer_add_extend(
DnsAnswer **a,
DnsResourceRecord *rr,
int ifindex,
DnsAnswerFlags flags,
DnsResourceRecord *rrsig) {
int r;
assert(a);
assert(rr);
r = dns_answer_reserve_or_clone(a, 1);
if (r < 0)
return r;
return dns_answer_add(*a, rr, ifindex, flags, rrsig);
}
int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl, int ifindex) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *soa = NULL;
soa = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_SOA, name);
if (!soa)
return -ENOMEM;
soa->ttl = ttl;
soa->soa.mname = strdup(name);
if (!soa->soa.mname)
return -ENOMEM;
soa->soa.rname = strjoin("root.", name);
if (!soa->soa.rname)
return -ENOMEM;
soa->soa.serial = 1;
soa->soa.refresh = 1;
soa->soa.retry = 1;
soa->soa.expire = 1;
soa->soa.minimum = ttl;
return dns_answer_add(a, soa, ifindex, DNS_ANSWER_AUTHENTICATED, NULL);
}
int dns_answer_match_key(DnsAnswer *a, const DnsResourceKey *key, DnsAnswerFlags *ret_flags) {
DnsAnswerFlags flags = 0, i_flags;
DnsResourceRecord *i;
bool found = false;
int r;
assert(key);
DNS_ANSWER_FOREACH_FLAGS(i, i_flags, a) {
r = dns_resource_key_match_rr(key, i, NULL);
if (r < 0)
return r;
if (r == 0)
continue;
if (!ret_flags)
return 1;
if (found)
flags &= i_flags;
else {
flags = i_flags;
found = true;
}
}
if (ret_flags)
*ret_flags = flags;
return found;
}
bool dns_answer_contains_nsec_or_nsec3(DnsAnswer *a) {
DnsResourceRecord *i;
DNS_ANSWER_FOREACH(i, a)
if (IN_SET(i->key->type, DNS_TYPE_NSEC, DNS_TYPE_NSEC3))
return true;
return false;
}
int dns_answer_contains_zone_nsec3(DnsAnswer *answer, const char *zone) {
DnsResourceRecord *rr;
int r;
/* Checks whether the specified answer contains at least one NSEC3 RR in the specified zone */
DNS_ANSWER_FOREACH(rr, answer) {
const char *p;
if (rr->key->type != DNS_TYPE_NSEC3)
continue;
p = dns_resource_key_name(rr->key);
r = dns_name_parent(&p);
if (r < 0)
return r;
if (r == 0)
continue;
r = dns_name_equal(p, zone);
if (r != 0)
return r;
}
return false;
}
bool dns_answer_contains(DnsAnswer *answer, DnsResourceRecord *rr) {
DnsResourceRecord *i;
DNS_ANSWER_FOREACH(i, answer)
if (dns_resource_record_equal(i, rr))
return true;
return false;
}
int dns_answer_find_soa(
DnsAnswer *a,
const DnsResourceKey *key,
DnsResourceRecord **ret,
DnsAnswerFlags *ret_flags) {
DnsResourceRecord *rr, *soa = NULL;
DnsAnswerFlags rr_flags, soa_flags = 0;
int r;
assert(key);
/* For a SOA record we can never find a matching SOA record */
if (key->type == DNS_TYPE_SOA)
goto not_found;
DNS_ANSWER_FOREACH_FLAGS(rr, rr_flags, a) {
r = dns_resource_key_match_soa(key, rr->key);
if (r < 0)
return r;
if (r > 0) {
if (soa) {
r = dns_name_endswith(dns_resource_key_name(rr->key), dns_resource_key_name(soa->key));
if (r < 0)
return r;
if (r > 0)
continue;
}
soa = rr;
soa_flags = rr_flags;
}
}
if (!soa)
goto not_found;
if (ret)
*ret = soa;
if (ret_flags)
*ret_flags = soa_flags;
return 1;
not_found:
if (ret)
*ret = NULL;
if (ret_flags)
*ret_flags = 0;
return 0;
}
int dns_answer_find_cname_or_dname(
DnsAnswer *a,
const DnsResourceKey *key,
DnsResourceRecord **ret,
DnsAnswerFlags *ret_flags) {
DnsResourceRecord *rr;
DnsAnswerFlags rr_flags;
int r;
assert(key);
/* For a {C,D}NAME record we can never find a matching {C,D}NAME record */
if (!dns_type_may_redirect(key->type))
return 0;
DNS_ANSWER_FOREACH_FLAGS(rr, rr_flags, a) {
r = dns_resource_key_match_cname_or_dname(key, rr->key, NULL);
if (r < 0)
return r;
if (r > 0) {
if (ret)
*ret = rr;
if (ret_flags)
*ret_flags = rr_flags;
return 1;
}
}
if (ret)
*ret = NULL;
if (ret_flags)
*ret_flags = 0;
return 0;
}
int dns_answer_merge(DnsAnswer *a, DnsAnswer *b, DnsAnswer **ret) {
_cleanup_(dns_answer_unrefp) DnsAnswer *k = NULL;
int r;
assert(ret);
if (a == b) {
*ret = dns_answer_ref(a);
return 0;
}
if (dns_answer_size(a) <= 0) {
*ret = dns_answer_ref(b);
return 0;
}
if (dns_answer_size(b) <= 0) {
*ret = dns_answer_ref(a);
return 0;
}
k = dns_answer_new(a->n_rrs + b->n_rrs);
if (!k)
return -ENOMEM;
r = dns_answer_add_raw_all(k, a);
if (r < 0)
return r;
r = dns_answer_add_all(k, b);
if (r < 0)
return r;
*ret = TAKE_PTR(k);
return 0;
}
int dns_answer_extend(DnsAnswer **a, DnsAnswer *b) {
DnsAnswer *merged;
int r;
assert(a);
r = dns_answer_merge(*a, b, &merged);
if (r < 0)
return r;
dns_answer_unref(*a);
*a = merged;
return 0;
}
int dns_answer_remove_by_key(DnsAnswer **a, const DnsResourceKey *key) {
bool found = false, other = false;
DnsResourceRecord *rr;
size_t i;
int r;
assert(a);
assert(key);
/* Remove all entries matching the specified key from *a */
DNS_ANSWER_FOREACH(rr, *a) {
r = dns_resource_key_equal(rr->key, key);
if (r < 0)
return r;
if (r > 0)
found = true;
else
other = true;
if (found && other)
break;
}
if (!found)
return 0;
if (!other) {
*a = dns_answer_unref(*a); /* Return NULL for the empty answer */
return 1;
}
if ((*a)->n_ref > 1) {
_cleanup_(dns_answer_unrefp) DnsAnswer *copy = NULL;
DnsAnswerItem *item;
copy = dns_answer_new((*a)->n_rrs);
if (!copy)
return -ENOMEM;
DNS_ANSWER_FOREACH_ITEM(item, *a) {
r = dns_resource_key_equal(item->rr->key, key);
if (r < 0)
return r;
if (r > 0)
continue;
r = dns_answer_add_raw(copy, item->rr, item->ifindex, item->flags, item->rrsig);
if (r < 0)
return r;
}
dns_answer_unref(*a);
*a = TAKE_PTR(copy);
return 1;
}
/* Only a single reference, edit in-place */
i = 0;
for (;;) {
if (i >= (*a)->n_rrs)
break;
r = dns_resource_key_equal((*a)->items[i].rr->key, key);
if (r < 0)
return r;
if (r > 0) {
/* Kill this entry */
dns_resource_record_unref((*a)->items[i].rr);
dns_resource_record_unref((*a)->items[i].rrsig);
memmove((*a)->items + i, (*a)->items + i + 1, sizeof(DnsAnswerItem) * ((*a)->n_rrs - i - 1));
(*a)->n_rrs--;
continue;
} else
/* Keep this entry */
i++;
}
return 1;
}
int dns_answer_remove_by_rr(DnsAnswer **a, DnsResourceRecord *rm) {
bool found = false, other = false;
DnsResourceRecord *rr;
size_t i;
int r;
assert(a);
assert(rm);
/* Remove all entries matching the specified RR from *a */
DNS_ANSWER_FOREACH(rr, *a) {
r = dns_resource_record_equal(rr, rm);
if (r < 0)
return r;
if (r > 0)
found = true;
else
other = true;
if (found && other)
break;
}
if (!found)
return 0;
if (!other) {
*a = dns_answer_unref(*a); /* Return NULL for the empty answer */
return 1;
}
if ((*a)->n_ref > 1) {
_cleanup_(dns_answer_unrefp) DnsAnswer *copy = NULL;
DnsAnswerItem *item;
copy = dns_answer_new((*a)->n_rrs);
if (!copy)
return -ENOMEM;
DNS_ANSWER_FOREACH_ITEM(item, *a) {
r = dns_resource_record_equal(item->rr, rm);
if (r < 0)
return r;
if (r > 0)
continue;
r = dns_answer_add_raw(copy, item->rr, item->ifindex, item->flags, item->rrsig);
if (r < 0)
return r;
}
dns_answer_unref(*a);
*a = TAKE_PTR(copy);
return 1;
}
/* Only a single reference, edit in-place */
i = 0;
for (;;) {
if (i >= (*a)->n_rrs)
break;
r = dns_resource_record_equal((*a)->items[i].rr, rm);
if (r < 0)
return r;
if (r > 0) {
/* Kill this entry */
dns_resource_record_unref((*a)->items[i].rr);
dns_resource_record_unref((*a)->items[i].rrsig);
memmove((*a)->items + i, (*a)->items + i + 1, sizeof(DnsAnswerItem) * ((*a)->n_rrs - i - 1));
(*a)->n_rrs--;
continue;
} else
/* Keep this entry */
i++;
}
return 1;
}
int dns_answer_remove_by_answer_keys(DnsAnswer **a, DnsAnswer *b) {
_cleanup_(dns_resource_key_unrefp) DnsResourceKey *prev = NULL;
DnsAnswerItem *item;
int r;
/* Removes all items from '*a' that have a matching key in 'b' */
DNS_ANSWER_FOREACH_ITEM(item, b) {
if (prev && dns_resource_key_equal(item->rr->key, prev)) /* Skip this one, we already looked at it */
continue;
r = dns_answer_remove_by_key(a, item->rr->key);
if (r < 0)
return r;
/* Let's remember this entry's RR key, to optimize the loop a bit: if we have an RRset with
* more than one item then we don't need to remove the key multiple times */
dns_resource_key_unref(prev);
prev = dns_resource_key_ref(item->rr->key);
}
return 0;
}
int dns_answer_copy_by_key(
DnsAnswer **a,
DnsAnswer *source,
const DnsResourceKey *key,
DnsAnswerFlags or_flags,
DnsResourceRecord *rrsig) {
DnsAnswerItem *item;
int r;
assert(a);
assert(key);
/* Copy all RRs matching the specified key from source into *a */
DNS_ANSWER_FOREACH_ITEM(item, source) {
r = dns_resource_key_equal(item->rr->key, key);
if (r < 0)
return r;
if (r == 0)
continue;
/* Make space for at least one entry */
r = dns_answer_reserve_or_clone(a, 1);
if (r < 0)
return r;
r = dns_answer_add(*a, item->rr, item->ifindex, item->flags|or_flags, rrsig ?: item->rrsig);
if (r < 0)
return r;
}
return 0;
}
int dns_answer_move_by_key(
DnsAnswer **to,
DnsAnswer **from,
const DnsResourceKey *key,
DnsAnswerFlags or_flags,
DnsResourceRecord *rrsig) {
int r;
assert(to);
assert(from);
assert(key);
r = dns_answer_copy_by_key(to, *from, key, or_flags, rrsig);
if (r < 0)
return r;
return dns_answer_remove_by_key(from, key);
}
void dns_answer_order_by_scope(DnsAnswer *a, bool prefer_link_local) {
DnsAnswerItem *items;
size_t i, start, end;
if (!a)
return;
if (a->n_rrs <= 1)
return;
start = 0;
end = a->n_rrs-1;
/* RFC 4795, Section 2.6 suggests we should order entries
* depending on whether the sender is a link-local address. */
items = newa(DnsAnswerItem, a->n_rrs);
for (i = 0; i < a->n_rrs; i++) {
if (dns_resource_record_is_link_local_address(a->items[i].rr) != prefer_link_local)
/* Order address records that are not preferred to the end of the array */
items[end--] = a->items[i];
else
/* Order all other records to the beginning of the array */
items[start++] = a->items[i];
}
assert(start == end+1);
memcpy(a->items, items, sizeof(DnsAnswerItem) * a->n_rrs);
}
int dns_answer_reserve(DnsAnswer **a, size_t n_free) {
DnsAnswer *n;
assert(a);
if (n_free <= 0)
return 0;
if (*a) {
size_t ns;
int r;
if ((*a)->n_ref > 1)
return -EBUSY;
ns = (*a)->n_rrs;
assert(ns <= UINT16_MAX); /* Maximum number of RRs we can stick into a DNS packet section */
if (n_free > UINT16_MAX - ns) /* overflow check */
ns = UINT16_MAX;
else
ns += n_free;
if ((*a)->n_allocated >= ns)
return 0;
/* Allocate more than we need, but not more than UINT16_MAX */
if (ns <= UINT16_MAX/2)
ns *= 2;
else
ns = UINT16_MAX;
/* This must be done before realloc() below. Otherwise, the original DnsAnswer object
* may be broken. */
r = set_reserve((*a)->set_items, ns);
if (r < 0)
return r;
n = realloc(*a, offsetof(DnsAnswer, items) + sizeof(DnsAnswerItem) * ns);
if (!n)
return -ENOMEM;
n->n_allocated = ns;
/* Previously all items are stored in the set, and the enough memory area is allocated
* in the above. So set_put() in the below cannot fail. */
set_clear(n->set_items);
for (size_t i = 0; i < n->n_rrs; i++)
assert_se(set_put(n->set_items, &n->items[i]) > 0);
} else {
n = dns_answer_new(n_free);
if (!n)
return -ENOMEM;
}
*a = n;
return 0;
}
int dns_answer_reserve_or_clone(DnsAnswer **a, size_t n_free) {
int r;
assert(a);
/* Tries to extend the DnsAnswer object. And if that's not possible, since we are not the sole owner,
* then allocate a new, appropriately sized one. Either way, after this call the object will only
* have a single reference, and has room for at least the specified number of RRs. */
if (*a && (*a)->n_ref > 1) {
_cleanup_(dns_answer_unrefp) DnsAnswer *n = NULL;
size_t ns;
ns = (*a)->n_rrs;
assert(ns <= UINT16_MAX); /* Maximum number of RRs we can stick into a DNS packet section */
if (n_free > UINT16_MAX - ns) /* overflow check */
ns = UINT16_MAX;
else if (n_free > 0) { /* Increase size and double the result, just in case — except if the
* increase is specified as 0, in which case we just allocate the
* exact amount as before, under the assumption this is just a request
* to copy the answer. */
ns += n_free;
if (ns <= UINT16_MAX/2) /* overflow check */
ns *= 2;
else
ns = UINT16_MAX;
}
n = dns_answer_new(ns);
if (!n)
return -ENOMEM;
r = dns_answer_add_raw_all(n, *a);
if (r < 0)
return r;
dns_answer_unref(*a);
assert_se(*a = TAKE_PTR(n));
} else if (n_free > 0) {
r = dns_answer_reserve(a, n_free);
if (r < 0)
return r;
}
return 0;
}
/*
* This function is not used in the code base, but is useful when debugging. Do not delete.
*/
void dns_answer_dump(DnsAnswer *answer, FILE *f) {
DnsAnswerItem *item;
if (!f)
f = stdout;
DNS_ANSWER_FOREACH_ITEM(item, answer) {
const char *t;
fputc('\t', f);
t = dns_resource_record_to_string(item->rr);
if (!t) {
log_oom();
continue;
}
fputs(t, f);
fputs("\t;", f);
fprintf(f, " ttl=%" PRIu32, item->rr->ttl);
if (item->ifindex != 0)
fprintf(f, " ifindex=%i", item->ifindex);
if (item->rrsig)
fputs(" rrsig", f);
if (item->flags & DNS_ANSWER_AUTHENTICATED)
fputs(" authenticated", f);
if (item->flags & DNS_ANSWER_CACHEABLE)
fputs(" cacheable", f);
if (item->flags & DNS_ANSWER_SHARED_OWNER)
fputs(" shared-owner", f);
if (item->flags & DNS_ANSWER_CACHE_FLUSH)
fputs(" cache-flush", f);
if (item->flags & DNS_ANSWER_GOODBYE)
fputs(" goodbye", f);
if (item->flags & DNS_ANSWER_SECTION_ANSWER)
fputs(" section-answer", f);
if (item->flags & DNS_ANSWER_SECTION_AUTHORITY)
fputs(" section-authority", f);
if (item->flags & DNS_ANSWER_SECTION_ADDITIONAL)
fputs(" section-additional", f);
fputc('\n', f);
}
}
int dns_answer_has_dname_for_cname(DnsAnswer *a, DnsResourceRecord *cname) {
DnsResourceRecord *rr;
int r;
assert(cname);
/* Checks whether the answer contains a DNAME record that indicates that the specified CNAME record is
* synthesized from it */
if (cname->key->type != DNS_TYPE_CNAME)
return 0;
DNS_ANSWER_FOREACH(rr, a) {
_cleanup_free_ char *n = NULL;
if (rr->key->type != DNS_TYPE_DNAME)
continue;
if (rr->key->class != cname->key->class)
continue;
r = dns_name_change_suffix(cname->cname.name, rr->dname.name, dns_resource_key_name(rr->key), &n);
if (r < 0)
return r;
if (r == 0)
continue;
r = dns_name_equal(n, dns_resource_key_name(cname->key));
if (r < 0)
return r;
if (r > 0)
return 1;
}
return 0;
}
void dns_answer_randomize(DnsAnswer *a) {
size_t n;
/* Permutes the answer list randomly (Knuth shuffle) */
n = dns_answer_size(a);
if (n <= 1)
return;
for (size_t i = 0; i < n; i++) {
size_t k;
k = random_u64_range(n);
if (k == i)
continue;
SWAP_TWO(a->items[i], a->items[k]);
}
}
uint32_t dns_answer_min_ttl(DnsAnswer *a) {
uint32_t ttl = UINT32_MAX;
DnsResourceRecord *rr;
/* Return the smallest TTL of all RRs in this answer */
DNS_ANSWER_FOREACH(rr, a) {
/* Don't consider OPT (where the TTL field is used for other purposes than an actual TTL) */
if (dns_type_is_pseudo(rr->key->type) ||
dns_class_is_pseudo(rr->key->class))
continue;
ttl = MIN(ttl, rr->ttl);
}
return ttl;
}
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