[dns] Append local domain to relative names

Try to qualify relative names in the DNS resolver using the DHCP Domain
Name.  For example:

  DHCP Domain Name: etherboot.org
  (Relative) Name: www

yields:

  www.etherboot.org

Only names with no dots ('.') will be modified.  A name with one or more
dots is unchanged.

diff --git a/src/include/gpxe/settings.h b/src/include/gpxe/settings.h
index e9f0bce..60244d3 100644 (file)
--- a/src/include/gpxe/settings.h
+++ b/src/include/gpxe/settings.h
@@ -218,6 +218,7 @@ extern struct setting ip_setting __setting;
 extern struct setting netmask_setting __setting;
 extern struct setting gateway_setting __setting;
 extern struct setting dns_setting __setting;
+extern struct setting domain_setting __setting;
 extern struct setting hostname_setting __setting;
 extern struct setting filename_setting __setting;
 extern struct setting root_path_setting __setting;

diff --git a/src/net/udp/dns.c b/src/net/udp/dns.c
index 1bcdbc7..a498aef 100644 (file)
--- a/src/net/udp/dns.c
+++ b/src/net/udp/dns.c
@@ -22,6 +22,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdio.h>
 #include <errno.h>
 #include <byteswap.h>
 #include <gpxe/refcnt.h>
@@ -47,6 +48,9 @@ static struct sockaddr_tcpip nameserver = {
        .st_port = htons ( DNS_PORT ),
 };
 
+/** The local domain */
+static char *localdomain;
+
 /** A DNS request */
 struct dns_request {
        /** Reference counter */
@@ -179,6 +183,27 @@ static union dns_rr_info * dns_find_rr ( struct dns_request *dns,
        return NULL;
 }
 
+/**
+ * Append DHCP domain name if available and name is not fully qualified
+ *
+ * @v string           Name as a NUL-terminated string
+ * @ret fqdn           Fully-qualified domain name, malloc'd copy
+ *
+ * The caller must free fqdn which is allocated even if the name is already
+ * fully qualified.
+ */
+static char * dns_qualify_name ( const char *string ) {
+       char *fqdn;
+
+       /* Leave unchanged if already fully-qualified or no local domain */
+       if ( ( ! localdomain ) || ( strchr ( string, '.' ) != 0 ) )
+               return strdup ( string );
+
+       /* Append local domain to name */
+       asprintf ( &fqdn, "%s.%s", string, localdomain );
+       return fqdn;
+}
+
 /**
  * Convert a standard NUL-terminated string to a DNS name
  *
@@ -452,19 +477,30 @@ static struct xfer_interface_operations dns_socket_operations = {
 static int dns_resolv ( struct resolv_interface *resolv,
                        const char *name, struct sockaddr *sa ) {
        struct dns_request *dns;
+       char *fqdn;
        int rc;
 
        /* Fail immediately if no DNS servers */
        if ( ! nameserver.st_family ) {
                DBG ( "DNS not attempting to resolve \"%s\": "
                      "no DNS servers\n", name );
-               return -ENXIO;
+               rc = -ENXIO;
+               goto err_no_nameserver;
+       }
+
+       /* Ensure fully-qualified domain name if DHCP option was given */
+       fqdn = dns_qualify_name ( name );
+       if ( ! fqdn ) {
+               rc = -ENOMEM;
+               goto err_qualify_name;
        }
 
        /* Allocate DNS structure */
        dns = zalloc ( sizeof ( *dns ) );
-       if ( ! dns )
-               return -ENOMEM;
+       if ( ! dns ) {
+               rc = -ENOMEM;
+               goto err_alloc_dns;
+       }
        resolv_init ( &dns->resolv, &null_resolv_ops, &dns->refcnt );
        xfer_init ( &dns->socket, &dns_socket_operations, &dns->refcnt );
        dns->timer.expired = dns_timer_expired;
@@ -474,7 +510,7 @@ static int dns_resolv ( struct resolv_interface *resolv,
        dns->query.dns.flags = htons ( DNS_FLAG_QUERY | DNS_FLAG_OPCODE_QUERY |
                                       DNS_FLAG_RD );
        dns->query.dns.qdcount = htons ( 1 );
-       dns->qinfo = ( void * ) dns_make_name ( name, dns->query.payload );
+       dns->qinfo = ( void * ) dns_make_name ( fqdn, dns->query.payload );
        dns->qinfo->qtype = htons ( DNS_TYPE_A );
        dns->qinfo->qclass = htons ( DNS_CLASS_IN );
 
@@ -484,7 +520,7 @@ static int dns_resolv ( struct resolv_interface *resolv,
                                       NULL ) ) != 0 ) {
                DBGC ( dns, "DNS %p could not open socket: %s\n",
                       dns, strerror ( rc ) );
-               goto err;
+               goto err_open_socket;
        }
 
        /* Send first DNS packet */
@@ -493,10 +529,15 @@ static int dns_resolv ( struct resolv_interface *resolv,
        /* Attach parent interface, mortalise self, and return */
        resolv_plug_plug ( &dns->resolv, resolv );
        ref_put ( &dns->refcnt );
+       free ( fqdn );
        return 0;       
 
- err:
+ err_open_socket:
+ err_alloc_dns:
        ref_put ( &dns->refcnt );
+ err_qualify_name:
+       free ( fqdn );
+ err_no_nameserver:
        return rc;
 }
 
@@ -521,12 +562,20 @@ struct setting dns_setting __setting = {
        .type = &setting_type_ipv4,
 };
 
+/** Domain name setting */
+struct setting domain_setting __setting = {
+       .name = "domain",
+       .description = "Local domain",
+       .tag = DHCP_DOMAIN_NAME,
+       .type = &setting_type_string,
+};
+
 /**
- * Apply nameserver setting
+ * Apply DNS settings
  *
  * @ret rc             Return status code
  */
-static int apply_nameserver_setting ( void ) {
+static int apply_dns_settings ( void ) {
        struct sockaddr_in *sin_nameserver =
                ( struct sockaddr_in * ) &nameserver;
        int len;
@@ -538,10 +587,15 @@ static int apply_nameserver_setting ( void ) {
                      inet_ntoa ( sin_nameserver->sin_addr ) );
        }
 
+       /* Get local domain DHCP option */
+       if ( ( len = fetch_string_setting_copy ( NULL, &domain_setting,
+                                                &localdomain ) ) >= 0 )
+               DBG ( "DNS local domain %s\n", localdomain );
+
        return 0;
 }
 
-/** Nameserver setting applicator */
-struct settings_applicator nameserver_applicator __settings_applicator = {
-       .apply = apply_nameserver_setting,
+/** DNS settings applicator */
+struct settings_applicator dns_applicator __settings_applicator = {
+       .apply = apply_dns_settings,
 };