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