MINOR: dns: Implement `parse-resolv-conf` directive

This introduces a new directive for the `resolvers` section:
`parse-resolv-conf`. When present, it will attempt to add any
nameservers in `/etc/resolv.conf` to the list of nameservers
for the current `resolvers` section.

[Mailing list thread][1].

[1]: https://www.mail-archive.com/haproxy@formilux.org/msg29600.html

diff --git a/doc/configuration.txt b/doc/configuration.txt
index e27d66627fedd37e8f29bcfa50a5e0d73a45179f..e901d7eeafd8ff00e0da25b30754cab5c2ff8007 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -12042,6 +12042,11 @@ nameserver <id> <ip>:<port>
     <ip>   : IP address of the server
     <port> : port where the DNS service actually runs
 
+parse-resolv-conf
+  Adds all nameservers found in /etc/resolv.conf to this resolvers nameservers
+  list. Ordered as if each nameserver in /etc/resolv.conf was individually
+  placed in the resolvers section in place of this directive.
+
 hold <status> <period>
   Defines <period> during which the last name resolution should be kept based
   on last resolution <status>
@@ -12085,6 +12090,7 @@ timeout <event> <time>
    resolvers mydns
      nameserver dns1 10.0.0.1:53
      nameserver dns2 10.0.0.2:53
+     parse-resolv-conf
      resolve_retries       3
      timeout resolve       1s
      timeout retry         1s

diff --git a/src/cfgparse.c b/src/cfgparse.c
index 3d224b9bee0d3fe93c81b6d04fd982d79e395bb4..f3c2be49901f6154ef1e48d8ad9d222e5ce84ff6 100644 (file)
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -2256,7 +2256,7 @@ int cfg_parse_resolvers(const char *file, int linenum, char **args, int kwm)
                        /* Error if two resolvers owns the same name */
                        if (strcmp(newnameserver->id, args[1]) == 0) {
                                ha_alert("Parsing [%s:%d]: nameserver '%s' has same name as another nameserver (declared at %s:%d).\n",
-                                        file, linenum, args[1], curr_resolvers->conf.file, curr_resolvers->conf.line);
+                                        file, linenum, args[1], newnameserver->conf.file, newnameserver->conf.line);
                                err_code |= ERR_ALERT | ERR_FATAL;
                        }
                }
@@ -2305,6 +2305,119 @@ int cfg_parse_resolvers(const char *file, int linenum, char **args, int kwm)
 
                newnameserver->addr = *sk;
        }
+       else if (strcmp(args[0], "parse-resolv-conf") == 0) {
+               const char *whitespace = "\r\n\t ";
+               char *resolv_line = NULL;
+               int resolv_linenum = 0;
+               FILE *f = NULL;
+               char *address = NULL;
+               struct sockaddr_storage *sk = NULL;
+               struct protocol *proto;
+               int duplicate_name = 0;
+
+               if ((resolv_line = malloc(sizeof(*resolv_line) * LINESIZE)) == NULL) {
+                       ha_alert("parsing [%s:%d] : out of memory.\n",
+                                file, linenum);
+                       err_code |= ERR_ALERT | ERR_FATAL;
+                       goto resolv_out;
+               }
+
+               if ((f = fopen("/etc/resolv.conf", "r")) == NULL) {
+                       ha_alert("parsing [%s:%d] : failed to open /etc/resolv.conf.\n",
+                                file, linenum);
+                       err_code |= ERR_ALERT | ERR_FATAL;
+                       goto resolv_out;
+               }
+
+               sk = calloc(1, sizeof(*sk));
+               if (sk == NULL) {
+                       ha_alert("parsing [/etc/resolv.conf:%d] : out of memory.\n",
+                                resolv_linenum);
+                       err_code |= ERR_ALERT | ERR_FATAL;
+                       goto resolv_out;
+               }
+
+               while (fgets(resolv_line, LINESIZE, f) != NULL) {
+                       resolv_linenum++;
+                       if (strncmp(resolv_line, "nameserver", 10) != 0)
+                               continue;
+
+                       address = strtok(resolv_line + 10, whitespace);
+                       if (address == resolv_line + 10)
+                               continue;
+
+                       if (address == NULL) {
+                               ha_warning("parsing [/etc/resolv.conf:%d] : nameserver line is missing address.\n",
+                                          resolv_linenum);
+                               err_code |= ERR_WARN;
+                               continue;
+                       }
+
+                       duplicate_name = 0;
+                       list_for_each_entry(newnameserver, &curr_resolvers->nameservers, list) {
+                               if (strcmp(newnameserver->id, address) == 0) {
+                                       ha_warning("Parsing [/etc/resolv.conf:%d] : generated name for /etc/resolv.conf nameserver '%s' conflicts with another nameserver (declared at %s:%d), it appears to be a duplicate and will be excluded.\n",
+                                                resolv_linenum, address, newnameserver->conf.file, newnameserver->conf.line);
+                                       err_code |= ERR_WARN;
+                                       duplicate_name = 1;
+                               }
+                       }
+
+                       if (duplicate_name)
+                               continue;
+
+                       memset(sk, 0, sizeof(*sk));
+                       sk = str2ip2(address, sk, 1);
+                       if (!sk) {
+                               ha_warning("parsing [/etc/resolv.conf:%d] : address '%s' could not be recognized, namerserver will be excluded.\n",
+                                          resolv_linenum, address);
+                               err_code |= ERR_WARN;
+                               continue;
+                       }
+
+                       set_host_port(sk, 53);
+
+                       proto = protocol_by_family(sk->ss_family);
+                       if (!proto || !proto->connect) {
+                               ha_warning("parsing [/etc/resolv.conf:%d] : '%s' : connect() not supported for this address family.\n",
+                                          resolv_linenum, address);
+                               err_code |= ERR_WARN;
+                               continue;
+                       }
+
+                       if ((newnameserver = calloc(1, sizeof(*newnameserver))) == NULL) {
+                               ha_alert("parsing [/etc/resolv.conf:%d] : out of memory.\n", resolv_linenum);
+                               err_code |= ERR_ALERT | ERR_FATAL;
+                               goto resolv_out;
+                       }
+
+                       newnameserver->conf.file = strdup("/etc/resolv.conf");
+                       if (newnameserver->conf.file == NULL) {
+                               ha_alert("parsing [/etc/resolv.conf:%d] : out of memory.\n", resolv_linenum);
+                               err_code |= ERR_ALERT | ERR_FATAL;
+                               goto resolv_out;
+                       }
+
+                       newnameserver->id = strdup(address);
+                       if (newnameserver->id == NULL) {
+                               ha_alert("parsing [/etc/resolv.conf:%d] : out of memory.\n", resolv_linenum);
+                               err_code |= ERR_ALERT | ERR_FATAL;
+                               goto resolv_out;
+                       }
+
+                       newnameserver->resolvers = curr_resolvers;
+                       newnameserver->conf.line = resolv_linenum;
+                       newnameserver->addr = *sk;
+
+                       LIST_ADDQ(&curr_resolvers->nameservers, &newnameserver->list);
+               }
+
+resolv_out:
+               free(sk);
+               free(resolv_line);
+               if (f != NULL)
+                       fclose(f);
+       }
        else if (strcmp(args[0], "hold") == 0) { /* hold periods */
                const char *res;
                unsigned int time;