resolved: beef up DNS server configuration logic

We now maintain two lists of DNS servers: system servers and fallback
servers.

system servers are used in combination with any per-link servers.

fallback servers are only used if there are no system servers or
per-link servers configured.

The system server list is supposed to be populated from a foreign tool's
/etc/resolv.conf (not implemented yet).

Also adds a configuration switch for LLMNR, that allows configuring
whether LLMNR shall be used simply for resolving or also for responding.

1 files changed, 157 insertions, 0 deletions

diff --git a/src/resolve/resolved-conf.c b/src/resolve/resolved-conf.c
new file mode 100644
index 0000000000..0def80e3a5
--- /dev/null
+++ b/src/resolve/resolved-conf.c
@@ -0,0 +1,157 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Tom Gundersen <teg@jklm.no>
+
+  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 "conf-parser.h"
+
+#include "resolved-conf.h"
+
+int manager_parse_dns_server(Manager *m, DnsServerType type, const char *string) {
+        const char *word, *state;
+        size_t length;
+        DnsServer *first;
+        int r;
+
+        assert(m);
+        assert(string);
+
+        first = type == DNS_SERVER_FALLBACK ? m->fallback_dns_servers : m->dns_servers;
+
+        FOREACH_WORD_QUOTED(word, length, string, state) {
+                char buffer[length+1];
+                int family;
+                union in_addr_union addr;
+                bool found = false;
+                DnsServer *s;
+
+                memcpy(buffer, word, length);
+                buffer[length] = 0;
+
+                r = in_addr_from_string_auto(buffer, &family, &addr);
+                if (r < 0) {
+                        log_warning("Ignoring invalid DNS address '%s'", buffer);
+                        continue;
+                }
+
+                /* Filter out duplicates */
+                LIST_FOREACH(servers, s, first)
+                        if (s->family == family && in_addr_equal(family, &s->address, &addr)) {
+                                found = true;
+                                break;
+                        }
+
+                if (found)
+                        continue;
+
+                r = dns_server_new(m, NULL, type, NULL, family, &addr);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int config_parse_dnsv(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Manager *m = userdata;
+        DnsServer **l;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(m);
+
+        if (ltype == DNS_SERVER_FALLBACK)
+                l = &m->fallback_dns_servers;
+        else
+                l = &m->dns_servers;
+
+        /* Empty assignment means clear the list */
+        if (isempty(rvalue)) {
+                while (*l)
+                        dns_server_free(*l);
+
+                return 0;
+        }
+
+        r = manager_parse_dns_server(m, ltype, rvalue);
+        if (r < 0) {
+                log_syntax(unit, LOG_ERR, filename, line, -r, "Failed to parse DNS server string '%s'. Ignoring.", rvalue);
+                return 0;
+        }
+
+        return 0;
+}
+
+int config_parse_support(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Manager *m = userdata;
+        Support support, *v = data;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(m);
+
+        support = support_from_string(rvalue);
+        if (support < 0) {
+                r = parse_boolean(rvalue);
+                if (r < 0) {
+                        log_syntax(unit, LOG_ERR, filename, line, -r, "Failed to parse support level '%s'. Ignoring.", rvalue);
+                        return 0;
+                }
+
+                support = r ? SUPPORT_YES : SUPPORT_NO;
+        }
+
+        *v = support;
+        return 0;
+}
+
+int manager_parse_config_file(Manager *m) {
+        assert(m);
+
+        return config_parse(NULL, "/etc/systemd/resolved.conf", NULL,
+                            "Resolve\0",
+                            config_item_perf_lookup, resolved_gperf_lookup,
+                            false, false, true, m);
+}