slirp: Add domainname option to slirp's DHCP server

This patch will allow the user to include the domainname option in
replies from the built-in DHCP server.

Signed-off-by: Benjamin Drung <benjamin.drung@profitbricks.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

net/slirp.c

@@ -157,7 +157,8 @@ static int net_slirp_init(NetClientState *peer, const char *model,
                           const char *bootfile, const char *vdhcp_start,
                           const char *vnameserver, const char *vnameserver6,
                           const char *smb_export, const char *vsmbserver,
-                          const char **dnssearch, Error **errp)
+                          const char **dnssearch, const char *vdomainname,
+                          Error **errp)
 {
     /* default settings according to historic slirp */
     struct in_addr net  = { .s_addr = htonl(0x0a000200) }; /* 10.0.2.0 */
@@ -359,6 +360,11 @@ static int net_slirp_init(NetClientState *peer, const char *model,
         ip6_dns.s6_addr[15] |= 3;
     }
 
+    if (vdomainname && !*vdomainname) {
+        error_setg(errp, "'domainname' parameter cannot be empty");
+        return -1;
+    }
+
 
     nc = qemu_new_net_client(&net_slirp_info, peer, model, name);
 
@@ -371,7 +377,7 @@ static int net_slirp_init(NetClientState *peer, const char *model,
     s->slirp = slirp_init(restricted, ipv4, net, mask, host,
                           ipv6, ip6_prefix, vprefix6_len, ip6_host,
                           vhostname, tftp_export, bootfile, dhcp,
-                          dns, ip6_dns, dnssearch, s);
+                          dns, ip6_dns, dnssearch, vdomainname, s);
     QTAILQ_INSERT_TAIL(&slirp_stacks, s, entry);
 
     for (config = slirp_configs; config; config = config->next) {
@@ -958,7 +964,7 @@ int net_init_slirp(const Netdev *netdev, const char *name,
                          user->ipv6_host, user->hostname, user->tftp,
                          user->bootfile, user->dhcpstart,
                          user->dns, user->ipv6_dns, user->smb,
-                         user->smbserver, dnssearch, errp);
+                         user->smbserver, dnssearch, user->domainname, errp);
 
     while (slirp_configs) {
         config = slirp_configs;

qapi/net.json

@@ -160,6 +160,9 @@
 # @dnssearch: list of DNS suffixes to search, passed as DHCP option
 #             to the guest
 #
+# @domainname: guest-visible domain name of the virtual nameserver
+#              (since 2.12)
+#
 # @ipv6-prefix: IPv6 network prefix (default is fec0::) (since
 #               2.6). The network prefix is given in the usual
 #               hexadecimal IPv6 address notation.
@@ -197,6 +200,7 @@
     '*dhcpstart': 'str',
     '*dns':       'str',
     '*dnssearch': ['String'],
+    '*domainname': 'str',
     '*ipv6-prefix':      'str',
     '*ipv6-prefixlen':   'int',
     '*ipv6-host':        'str',

qemu-options.hx

@@ -1906,8 +1906,8 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
     "-netdev user,id=str[,ipv4[=on|off]][,net=addr[/mask]][,host=addr]\n"
     "         [,ipv6[=on|off]][,ipv6-net=addr[/int]][,ipv6-host=addr]\n"
     "         [,restrict=on|off][,hostname=host][,dhcpstart=addr]\n"
-    "         [,dns=addr][,ipv6-dns=addr][,dnssearch=domain][,tftp=dir]\n"
+    "         [,dns=addr][,ipv6-dns=addr][,dnssearch=domain][,domainname=domain]\n"
-    "         [,bootfile=f][,hostfwd=rule][,guestfwd=rule]"
+    "         [,tftp=dir][,bootfile=f][,hostfwd=rule][,guestfwd=rule]"
 #ifndef _WIN32
                                              "[,smb=dir[,smbserver=addr]]\n"
 #endif
@@ -2135,6 +2135,9 @@ Example:
 qemu-system-i386 -nic user,dnssearch=mgmt.example.org,dnssearch=example.org
 @end example
 
+@item domainname=@var{domain}
+Specifies the client domain name reported by the built-in DHCP server.
+
 @item tftp=@var{dir}
 When using the user mode network stack, activate a built-in TFTP
 server. The files in @var{dir} will be exposed as the root of a TFTP server.

slirp/bootp.c

@@ -298,6 +298,14 @@ static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
             q += val;
         }
 
+        if (slirp->vdomainname) {
+            val = strlen(slirp->vdomainname);
+            *q++ = RFC1533_DOMAINNAME;
+            *q++ = val;
+            memcpy(q, slirp->vdomainname, val);
+            q += val;
+        }
+
         if (slirp->vdnssearch) {
             size_t spaceleft = sizeof(rbp->bp_vend) - (q - rbp->bp_vend);
             val = slirp->vdnssearch_len;

slirp/libslirp.h

@@ -16,7 +16,7 @@ Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
                   const char *tftp_path, const char *bootfile,
                   struct in_addr vdhcp_start, struct in_addr vnameserver,
                   struct in6_addr vnameserver6, const char **vdnssearch,
-                  void *opaque);
+                  const char *vdomainname, void *opaque);
 void slirp_cleanup(Slirp *slirp);
 
 void slirp_pollfds_fill(GArray *pollfds, uint32_t *timeout);

slirp/slirp.c

@@ -286,7 +286,7 @@ Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
                   const char *tftp_path, const char *bootfile,
                   struct in_addr vdhcp_start, struct in_addr vnameserver,
                   struct in6_addr vnameserver6, const char **vdnssearch,
-                  void *opaque)
+                  const char *vdomainname, void *opaque)
 {
     Slirp *slirp = g_malloc0(sizeof(Slirp));
 
@@ -317,6 +317,7 @@ Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
     }
     slirp->tftp_prefix = g_strdup(tftp_path);
     slirp->bootp_filename = g_strdup(bootfile);
+    slirp->vdomainname = g_strdup(vdomainname);
     slirp->vdhcp_startaddr = vdhcp_start;
     slirp->vnameserver_addr = vnameserver;
     slirp->vnameserver_addr6 = vnameserver6;
@@ -349,6 +350,7 @@ void slirp_cleanup(Slirp *slirp)
     g_free(slirp->vdnssearch);
     g_free(slirp->tftp_prefix);
     g_free(slirp->bootp_filename);
+    g_free(slirp->vdomainname);
     g_free(slirp);
 }
 

slirp/slirp.h

@@ -193,6 +193,7 @@ struct Slirp {
     char *bootp_filename;
     size_t vdnssearch_len;
     uint8_t *vdnssearch;
+    char *vdomainname;
 
     /* tcp states */
     struct socket tcb;