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Systemd/src/resolve/resolved-etc-hosts.c
Zbigniew Jędrzejewski-Szmek ca78ad1de9 headers: remove unneeded includes from util.h 
This means we need to include many more headers in various files that simply
included util.h before, but it seems cleaner to do it this way.
2019-03-27 11:53:12 +01:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "fd-util.h"
#include "fileio.h"
#include "hostname-util.h"
#include "resolved-dns-synthesize.h"
#include "resolved-etc-hosts.h"
#include "string-util.h"
#include "strv.h"
#include "time-util.h"
/* Recheck /etc/hosts at most once every 2s */
#define ETC_HOSTS_RECHECK_USEC (2*USEC_PER_SEC)
static void etc_hosts_item_free(EtcHostsItem *item) {
strv_free(item->names);
free(item);
}
static void etc_hosts_item_by_name_free(EtcHostsItemByName *item) {
free(item->name);
free(item->addresses);
free(item);
}
void etc_hosts_free(EtcHosts *hosts) {
hosts->by_address = hashmap_free_with_destructor(hosts->by_address, etc_hosts_item_free);
hosts->by_name = hashmap_free_with_destructor(hosts->by_name, etc_hosts_item_by_name_free);
hosts->no_address = set_free_free(hosts->no_address);
}
void manager_etc_hosts_flush(Manager *m) {
etc_hosts_free(&m->etc_hosts);
m->etc_hosts_mtime = USEC_INFINITY;
}
static int parse_line(EtcHosts *hosts, unsigned nr, const char *line) {
_cleanup_free_ char *address_str = NULL;
struct in_addr_data address = {};
bool found = false;
EtcHostsItem *item;
int r;
assert(hosts);
assert(line);
r = extract_first_word(&line, &address_str, NULL, EXTRACT_RELAX);
if (r < 0)
return log_error_errno(r, "/etc/hosts:%u: failed to extract address: %m", nr);
assert(r > 0); /* We already checked that the line is not empty, so it should contain *something* */
r = in_addr_ifindex_from_string_auto(address_str, &address.family, &address.address, NULL);
if (r < 0) {
log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str);
return 0;
}
r = in_addr_is_null(address.family, &address.address);
if (r < 0) {
log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str);
return 0;
}
if (r > 0)
/* This is an 0.0.0.0 or :: item, which we assume means that we shall map the specified hostname to
* nothing. */
item = NULL;
else {
/* If this is a normal address, then simply add entry mapping it to the specified names */
item = hashmap_get(hosts->by_address, &address);
if (!item) {
r = hashmap_ensure_allocated(&hosts->by_address, &in_addr_data_hash_ops);
if (r < 0)
return log_oom();
item = new0(EtcHostsItem, 1);
if (!item)
return log_oom();
item->address = address;
r = hashmap_put(hosts->by_address, &item->address, item);
if (r < 0) {
free(item);
return log_oom();
}
}
}
for (;;) {
_cleanup_free_ char *name = NULL;
EtcHostsItemByName *bn;
r = extract_first_word(&line, &name, NULL, EXTRACT_RELAX);
if (r < 0)
return log_error_errno(r, "/etc/hosts:%u: couldn't extract host name: %m", nr);
if (r == 0)
break;
found = true;
r = dns_name_is_valid_ldh(name);
if (r <= 0) {
log_warning_errno(r, "/etc/hosts:%u: hostname \"%s\" is not valid, ignoring.", nr, name);
continue;
}
if (is_localhost(name))
/* Suppress the "localhost" line that is often seen */
continue;
if (!item) {
/* Optimize the case where we don't need to store any addresses, by storing
* only the name in a dedicated Set instead of the hashmap */
r = set_ensure_allocated(&hosts->no_address, &dns_name_hash_ops);
if (r < 0)
return log_oom();
r = set_put(hosts->no_address, name);
if (r < 0)
return r;
TAKE_PTR(name);
continue;
}
r = strv_extend(&item->names, name);
if (r < 0)
return log_oom();
bn = hashmap_get(hosts->by_name, name);
if (!bn) {
r = hashmap_ensure_allocated(&hosts->by_name, &dns_name_hash_ops);
if (r < 0)
return log_oom();
bn = new0(EtcHostsItemByName, 1);
if (!bn)
return log_oom();
r = hashmap_put(hosts->by_name, name, bn);
if (r < 0) {
free(bn);
return log_oom();
}
bn->name = TAKE_PTR(name);
}
if (!GREEDY_REALLOC(bn->addresses, bn->n_allocated, bn->n_addresses + 1))
return log_oom();
bn->addresses[bn->n_addresses++] = &item->address;
}
if (!found)
log_warning("/etc/hosts:%u: line is missing any host names", nr);
return 0;
}
int etc_hosts_parse(EtcHosts *hosts, FILE *f) {
_cleanup_(etc_hosts_free) EtcHosts t = {};
unsigned nr = 0;
int r;
for (;;) {
_cleanup_free_ char *line = NULL;
char *l;
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0)
return log_error_errno(r, "Failed to read /etc/hosts: %m");
if (r == 0)
break;
nr++;
l = strchr(line, '#');
if (l)
*l = '\0';
l = strstrip(line);
if (isempty(l))
continue;
r = parse_line(&t, nr, l);
if (r < 0)
return r;
}
etc_hosts_free(hosts);
*hosts = t;
t = (EtcHosts) {}; /* prevent cleanup */
return 0;
}
static int manager_etc_hosts_read(Manager *m) {
_cleanup_fclose_ FILE *f = NULL;
struct stat st;
usec_t ts;
int r;
assert_se(sd_event_now(m->event, clock_boottime_or_monotonic(), &ts) >= 0);
/* See if we checked /etc/hosts recently already */
if (m->etc_hosts_last != USEC_INFINITY && m->etc_hosts_last + ETC_HOSTS_RECHECK_USEC > ts)
return 0;
m->etc_hosts_last = ts;
if (m->etc_hosts_mtime != USEC_INFINITY) {
if (stat("/etc/hosts", &st) < 0) {
if (errno != ENOENT)
return log_error_errno(errno, "Failed to stat /etc/hosts: %m");
manager_etc_hosts_flush(m);
return 0;
}
/* Did the mtime change? If not, there's no point in re-reading the file. */
if (timespec_load(&st.st_mtim) == m->etc_hosts_mtime)
return 0;
}
f = fopen("/etc/hosts", "re");
if (!f) {
if (errno != ENOENT)
return log_error_errno(errno, "Failed to open /etc/hosts: %m");
manager_etc_hosts_flush(m);
return 0;
}
/* Take the timestamp at the beginning of processing, so that any changes made later are read on the next
* invocation */
r = fstat(fileno(f), &st);
if (r < 0)
return log_error_errno(errno, "Failed to fstat() /etc/hosts: %m");
r = etc_hosts_parse(&m->etc_hosts, f);
if (r < 0)
return r;
m->etc_hosts_mtime = timespec_load(&st.st_mtim);
m->etc_hosts_last = ts;
return 1;
}
int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer) {
bool found_a = false, found_aaaa = false;
struct in_addr_data k = {};
EtcHostsItemByName *bn;
DnsResourceKey *t;
const char *name;
unsigned i;
int r;
assert(m);
assert(q);
assert(answer);
if (!m->read_etc_hosts)
return 0;
(void) manager_etc_hosts_read(m);
name = dns_question_first_name(q);
if (!name)
return 0;
r = dns_name_address(name, &k.family, &k.address);
if (r > 0) {
EtcHostsItem *item;
DnsResourceKey *found_ptr = NULL;
item = hashmap_get(m->etc_hosts.by_address, &k);
if (!item)
return 0;
/* We have an address in /etc/hosts that matches the queried name. Let's return successful. Actual data
* we'll only return if the request was for PTR. */
DNS_QUESTION_FOREACH(t, q) {
if (!IN_SET(t->type, DNS_TYPE_PTR, DNS_TYPE_ANY))
continue;
if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY))
continue;
r = dns_name_equal(dns_resource_key_name(t), name);
if (r < 0)
return r;
if (r > 0) {
found_ptr = t;
break;
}
}
if (found_ptr) {
char **n;
r = dns_answer_reserve(answer, strv_length(item->names));
if (r < 0)
return r;
STRV_FOREACH(n, item->names) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
rr = dns_resource_record_new(found_ptr);
if (!rr)
return -ENOMEM;
rr->ptr.name = strdup(*n);
if (!rr->ptr.name)
return -ENOMEM;
r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
}
}
return 1;
}
bn = hashmap_get(m->etc_hosts.by_name, name);
if (bn) {
r = dns_answer_reserve(answer, bn->n_addresses);
if (r < 0)
return r;
} else {
/* Check if name was listed with no address. If yes, continue to return an answer. */
if (!set_contains(m->etc_hosts.no_address, name))
return 0;
}
DNS_QUESTION_FOREACH(t, q) {
if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA, DNS_TYPE_ANY))
continue;
if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY))
continue;
r = dns_name_equal(dns_resource_key_name(t), name);
if (r < 0)
return r;
if (r == 0)
continue;
if (IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_ANY))
found_a = true;
if (IN_SET(t->type, DNS_TYPE_AAAA, DNS_TYPE_ANY))
found_aaaa = true;
if (found_a && found_aaaa)
break;
}
for (i = 0; bn && i < bn->n_addresses; i++) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
if ((!found_a && bn->addresses[i]->family == AF_INET) ||
(!found_aaaa && bn->addresses[i]->family == AF_INET6))
continue;
r = dns_resource_record_new_address(&rr, bn->addresses[i]->family, &bn->addresses[i]->address, bn->name);
if (r < 0)
return r;
r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
}
return found_a || found_aaaa;
}
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