DnsServer *manager_get_dns_server(Manager *m) {
Link *l;
assert(m);
/* Try to read updates resolv.conf */
manager_read_resolv_conf(m);
/* If no DNS server was chosen so far, pick the first one */
if (!m->current_dns_server)
manager_set_dns_server(m, m->dns_servers);
if (!m->current_dns_server) {
bool found = false;
Iterator i;
/* No DNS servers configured, let's see if there are
* any on any links. If not, we use the fallback
* servers */
HASHMAP_FOREACH(l, m->links, i)
if (l->dns_servers) {
found = true;
break;
}
if (!found)
manager_set_dns_server(m, m->fallback_dns_servers);
}
DnsServer* dns_server_free(DnsServer *s) {
if (!s)
return NULL;
if (s->manager) {
if (s->type == DNS_SERVER_LINK)
LIST_REMOVE(servers, s->link->dns_servers, s);
else if (s->type == DNS_SERVER_SYSTEM)
LIST_REMOVE(servers, s->manager->dns_servers, s);
else if (s->type == DNS_SERVER_FALLBACK)
LIST_REMOVE(servers, s->manager->fallback_dns_servers, s);
else
assert_not_reached("Unknown server type");
if (s->manager->current_dns_server == s)
manager_set_dns_server(s->manager, NULL);
}
if (s->link && s->link->current_dns_server == s)
link_set_dns_server(s->link, NULL);
free(s);
return NULL;
}
int dns_server_new(
Manager *m,
DnsServer **ret,
DnsServerType type,
Link *l,
int family,
const union in_addr_union *in_addr) {
DnsServer *s, *tail;
assert(m);
assert((type == DNS_SERVER_LINK) == !!l);
assert(in_addr);
s = new0(DnsServer, 1);
if (!s)
return -ENOMEM;
s->n_ref = 1;
s->type = type;
s->family = family;
s->address = *in_addr;
s->resend_timeout = DNS_TIMEOUT_MIN_USEC;
if (type == DNS_SERVER_LINK) {
LIST_FIND_TAIL(servers, l->dns_servers, tail);
LIST_INSERT_AFTER(servers, l->dns_servers, tail, s);
s->link = l;
} else if (type == DNS_SERVER_SYSTEM) {
LIST_FIND_TAIL(servers, m->dns_servers, tail);
LIST_INSERT_AFTER(servers, m->dns_servers, tail, s);
} else if (type == DNS_SERVER_FALLBACK) {
LIST_FIND_TAIL(servers, m->fallback_dns_servers, tail);
LIST_INSERT_AFTER(servers, m->fallback_dns_servers, tail, s);
} else
assert_not_reached("Unknown server type");
s->manager = m;
/* A new DNS server that isn't fallback is added and the one
* we used so far was a fallback one? Then let's try to pick
* the new one */
if (type != DNS_SERVER_FALLBACK &&
m->current_dns_server &&
m->current_dns_server->type == DNS_SERVER_FALLBACK)
manager_set_dns_server(m, NULL);
if (ret)
*ret = s;
return 0;
}
static DnsServer* dns_server_free(DnsServer *s) {
if (!s)
return NULL;
if (s->link && s->link->current_dns_server == s)
link_set_dns_server(s->link, NULL);
if (s->manager && s->manager->current_dns_server == s)
manager_set_dns_server(s->manager, NULL);
free(s);
return NULL;
}
void dns_server_unlink(DnsServer *s) {
assert(s);
assert(s->manager);
/* This removes the specified server from the linked list of
* servers, but any server might still stay around if it has
* refs, for example from an ongoing transaction. */
if (!s->linked)
return;
switch (s->type) {
case DNS_SERVER_LINK:
assert(s->link);
assert(s->link->n_dns_servers > 0);
LIST_REMOVE(servers, s->link->dns_servers, s);
s->link->n_dns_servers--;
break;
case DNS_SERVER_SYSTEM:
assert(s->manager->n_dns_servers > 0);
LIST_REMOVE(servers, s->manager->dns_servers, s);
s->manager->n_dns_servers--;
break;
case DNS_SERVER_FALLBACK:
assert(s->manager->n_dns_servers > 0);
LIST_REMOVE(servers, s->manager->fallback_dns_servers, s);
s->manager->n_dns_servers--;
break;
}
s->linked = false;
if (s->link && s->link->current_dns_server == s)
link_set_dns_server(s->link, NULL);
if (s->manager->current_dns_server == s)
manager_set_dns_server(s->manager, NULL);
dns_server_unref(s);
}
int dns_server_new(
Manager *m,
DnsServer **ret,
DnsServerType type,
Link *l,
int family,
const union in_addr_union *in_addr,
int ifindex) {
DnsServer *s;
assert(m);
assert((type == DNS_SERVER_LINK) == !!l);
assert(in_addr);
if (!IN_SET(family, AF_INET, AF_INET6))
return -EAFNOSUPPORT;
if (l) {
if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX)
return -E2BIG;
} else {
if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX)
return -E2BIG;
}
s = new0(DnsServer, 1);
if (!s)
return -ENOMEM;
s->n_ref = 1;
s->manager = m;
s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID;
s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST;
s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC;
s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX;
s->type = type;
s->family = family;
s->address = *in_addr;
s->ifindex = ifindex;
s->resend_timeout = DNS_TIMEOUT_MIN_USEC;
switch (type) {
case DNS_SERVER_LINK:
s->link = l;
LIST_APPEND(servers, l->dns_servers, s);
l->n_dns_servers++;
break;
case DNS_SERVER_SYSTEM:
LIST_APPEND(servers, m->dns_servers, s);
m->n_dns_servers++;
break;
case DNS_SERVER_FALLBACK:
LIST_APPEND(servers, m->fallback_dns_servers, s);
m->n_dns_servers++;
break;
default:
assert_not_reached("Unknown server type");
}
s->linked = true;
/* A new DNS server that isn't fallback is added and the one
* we used so far was a fallback one? Then let's try to pick
* the new one */
if (type != DNS_SERVER_FALLBACK &&
m->current_dns_server &&
m->current_dns_server->type == DNS_SERVER_FALLBACK)
manager_set_dns_server(m, NULL);
if (ret)
*ret = s;
return 0;
}
int manager_read_resolv_conf(Manager *m) {
_cleanup_fclose_ FILE *f = NULL;
struct stat st, own;
char line[LINE_MAX];
usec_t t;
int r;
assert(m);
/* Reads the system /etc/resolv.conf, if it exists and is not
* symlinked to our own resolv.conf instance */
if (!m->read_resolv_conf)
return 0;
r = stat("/etc/resolv.conf", &st);
if (r < 0) {
if (errno == ENOENT)
return 0;
r = log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m");
goto clear;
}
/* Have we already seen the file? */
t = timespec_load(&st.st_mtim);
if (t == m->resolv_conf_mtime)
return 0;
/* Is it symlinked to our own file? */
if (stat(PRIVATE_RESOLV_CONF, &own) >= 0 &&
st.st_dev == own.st_dev &&
st.st_ino == own.st_ino)
return 0;
f = fopen("/etc/resolv.conf", "re");
if (!f) {
if (errno == ENOENT)
return 0;
r = log_warning_errno(errno, "Failed to open /etc/resolv.conf: %m");
goto clear;
}
if (fstat(fileno(f), &st) < 0) {
r = log_error_errno(errno, "Failed to stat open file: %m");
goto clear;
}
dns_server_mark_all(m->dns_servers);
dns_search_domain_mark_all(m->search_domains);
FOREACH_LINE(line, f, r = -errno; goto clear) {
const char *a;
char *l;
l = strstrip(line);
if (IN_SET(*l, '#', ';'))
continue;
a = first_word(l, "nameserver");
if (a) {
r = manager_parse_dns_server_string_and_warn(m, DNS_SERVER_SYSTEM, a);
if (r < 0)
log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring.", a);
continue;
}
a = first_word(l, "domain");
if (!a) /* We treat "domain" lines, and "search" lines as equivalent, and add both to our list. */
a = first_word(l, "search");
if (a) {
r = manager_parse_search_domains_and_warn(m, a);
if (r < 0)
log_warning_errno(r, "Failed to parse search domain string '%s', ignoring.", a);
}
}
m->resolv_conf_mtime = t;
/* Flush out all servers and search domains that are still
* marked. Those are then ones that didn't appear in the new
* /etc/resolv.conf */
dns_server_unlink_marked(m->dns_servers);
dns_search_domain_unlink_marked(m->search_domains);
/* Whenever /etc/resolv.conf changes, start using the first
* DNS server of it. This is useful to deal with broken
* network managing implementations (like NetworkManager),
* that when connecting to a VPN place both the VPN DNS
* servers and the local ones in /etc/resolv.conf. Without
* resetting the DNS server to use back to the first entry we
* will continue to use the local one thus being unable to
* resolve VPN domains. */
manager_set_dns_server(m, m->dns_servers);
/* Unconditionally flush the cache when /etc/resolv.conf is
* modified, even if the data it contained was completely
* identical to the previous version we used. We do this
* because altering /etc/resolv.conf is typically done when
* the network configuration changes, and that should be
* enough to flush the global unicast DNS cache. */
if (m->unicast_scope)
dns_cache_flush(&m->unicast_scope->cache);
/* If /etc/resolv.conf changed, make sure to forget everything we learned about the DNS servers. After all we
* might now talk to a very different DNS server that just happens to have the same IP address as an old one
* (think 192.168.1.1). */
dns_server_reset_features_all(m->dns_servers);
return 0;
clear:
dns_server_unlink_all(m->dns_servers);
dns_search_domain_unlink_all(m->search_domains);
return r;
}
int dns_server_new(
Manager *m,
DnsServer **ret,
DnsServerType type,
Link *l,
int family,
const union in_addr_union *in_addr) {
DnsServer *s;
assert(m);
assert((type == DNS_SERVER_LINK) == !!l);
assert(in_addr);
if (!IN_SET(family, AF_INET, AF_INET6))
return -EAFNOSUPPORT;
if (l) {
if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX)
return -E2BIG;
} else {
if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX)
return -E2BIG;
}
s = new0(DnsServer, 1);
if (!s)
return -ENOMEM;
s->n_ref = 1;
s->manager = m;
s->type = type;
s->family = family;
s->address = *in_addr;
s->resend_timeout = DNS_TIMEOUT_MIN_USEC;
switch (type) {
case DNS_SERVER_LINK:
s->link = l;
LIST_APPEND(servers, l->dns_servers, s);
l->n_dns_servers++;
break;
case DNS_SERVER_SYSTEM:
LIST_APPEND(servers, m->dns_servers, s);
m->n_dns_servers++;
break;
case DNS_SERVER_FALLBACK:
LIST_APPEND(servers, m->fallback_dns_servers, s);
m->n_dns_servers++;
break;
default:
assert_not_reached("Unknown server type");
}
s->linked = true;
/* A new DNS server that isn't fallback is added and the one
* we used so far was a fallback one? Then let's try to pick
* the new one */
if (type != DNS_SERVER_FALLBACK &&
m->current_dns_server &&
m->current_dns_server->type == DNS_SERVER_FALLBACK)
manager_set_dns_server(m, NULL);
if (ret)
*ret = s;
return 0;
}
