[Qemu-devel] [PATCH] [slirp] add nextserver support in slirp's dhcp-server

[Bas van Sisseren <bas@quarantainenet.nl>]

The slirp dhcp-server normally returns its own address as tftp
nextserver for netbooting. This patch makes that address
configurable, so it is possible to use an external tftp boot-
environment.

Signed-off-by: Bas van Sisseren <bas@quarantainenet.nl>
---
 net/slirp.c      | 10 ++++++++--
 qapi-schema.json |  3 +++
 qemu-options.hx  |  5 ++++-
 slirp/bootp.c    |  6 +++++-
 slirp/libslirp.h |  1 +
 slirp/slirp.c    |  2 ++
 slirp/slirp.h    |  1 +
 7 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/net/slirp.c b/net/slirp.c
index 124e953..f3e239c 100644
--- a/net/slirp.c
+++ b/net/slirp.c
@@ -136,6 +136,7 @@ static int net_slirp_init(NetClientState *peer, const char *model,
                           const char *vnetwork, const char *vhost,
                           const char *vhostname, const char *tftp_export,
                           const char *bootfile, const char *vdhcp_start,
+                          const char *vnextserver,
                           const char *vnameserver, const char *smb_export,
                           const char *vsmbserver, const char **dnssearch)
 {
@@ -145,6 +146,7 @@ static int net_slirp_init(NetClientState *peer, const char *model,
     struct in_addr host = { .s_addr = htonl(0x0a000202) }; /* 10.0.2.2 */
     struct in_addr dhcp = { .s_addr = htonl(0x0a00020f) }; /* 10.0.2.15 */
     struct in_addr dns  = { .s_addr = htonl(0x0a000203) }; /* 10.0.2.3 */
+    struct in_addr nxtsrv = { .s_addr = 0 };
 #ifndef _WIN32
     struct in_addr smbsrv = { .s_addr = 0 };
 #endif
@@ -228,6 +230,10 @@ static int net_slirp_init(NetClientState *peer, const char *model,
         return -1;
     }
 
+    if (vnextserver && !inet_aton(vnextserver, &nxtsrv)) {
+        return -1;
+    }
+
 #ifndef _WIN32
     if (vsmbserver && !inet_aton(vsmbserver, &smbsrv)) {
         return -1;
@@ -243,7 +249,7 @@ static int net_slirp_init(NetClientState *peer, const char *model,
     s = DO_UPCAST(SlirpState, nc, nc);
 
     s->slirp = slirp_init(restricted, net, mask, host, vhostname,
-                          tftp_export, bootfile, dhcp, dns, dnssearch, s);
+                          tftp_export, bootfile, dhcp, nxtsrv, dns, dnssearch, s);
     QTAILQ_INSERT_TAIL(&slirp_stacks, s, entry);
 
     for (config = slirp_configs; config; config = config->next) {
@@ -751,7 +757,7 @@ int net_init_slirp(const NetClientOptions *opts, const char *name,
 
     ret = net_slirp_init(peer, "user", name, user->q_restrict, vnet,
                          user->host, user->hostname, user->tftp,
-                         user->bootfile, user->dhcpstart, user->dns, user->smb,
+                         user->bootfile, user->dhcpstart, user->nextserver, user->dns, user->smb,
                          user->smbserver, dnssearch);
 
     while (slirp_configs) {
diff --git a/qapi-schema.json b/qapi-schema.json
index a80ee40..a8e2c3d 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2537,6 +2537,8 @@
 # @dhcpstart: #optional the first of the 16 IPs the built-in DHCP server can
 #             assign
 #
+# @nextserver: #optional IP address of BOOTP server
+#
 # @dns: #optional guest-visible address of the virtual nameserver
 #
 # @dnssearch: #optional list of DNS suffixes to search, passed as DHCP option
@@ -2563,6 +2565,7 @@
     '*tftp':      'str',
     '*bootfile':  'str',
     '*dhcpstart': 'str',
+    '*nextserver': 'str',
     '*dns':       'str',
     '*dnssearch': ['String'],
     '*smb':       'str',
diff --git a/qemu-options.hx b/qemu-options.hx
index 8355f9b..8afe42a 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1350,7 +1350,7 @@ DEF("net", HAS_ARG, QEMU_OPTION_net,
 #ifdef CONFIG_SLIRP
     "-net user[,vlan=n][,name=str][,net=addr[/mask]][,host=addr][,restrict=on|off]\n"
     "         [,hostname=host][,dhcpstart=addr][,dns=addr][,dnssearch=domain][,tftp=dir]\n"
-    "         [,bootfile=f][,hostfwd=rule][,guestfwd=rule]"
+    "         [,bootfile=f][,nextserver=addr][,hostfwd=rule][,guestfwd=rule]"
 #ifndef _WIN32
                                              "[,smb=dir[,smbserver=addr]]\n"
 #endif
@@ -1498,6 +1498,9 @@ When using the user mode network stack, broadcast @var{file} as the BOOTP
 filename. In conjunction with @option{tftp}, this can be used to network boot
 a guest from a local directory.
 
+@item nextserver=@var{addr}
+Specify the IP address of the TFTP server.
+
 Example (using pxelinux):
 @example
 qemu-system-i386 -hda linux.img -boot n -net user,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
diff --git a/slirp/bootp.c b/slirp/bootp.c
index b7db9fa..d2e89d6 100644
--- a/slirp/bootp.c
+++ b/slirp/bootp.c
@@ -227,7 +227,11 @@ static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, ETH_ALEN);
 
     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
-    rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
+    if (slirp->vnext_server.s_addr == 0) {
+        rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
+    } else {
+        rbp->bp_siaddr = slirp->vnext_server; /* Next-Server address */
+    }
 
     q = rbp->bp_vend;
     memcpy(q, rfc1533_cookie, 4);
diff --git a/slirp/libslirp.h b/slirp/libslirp.h
index ceabff8..c3d800b 100644
--- a/slirp/libslirp.h
+++ b/slirp/libslirp.h
@@ -12,6 +12,7 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
                   struct in_addr vnetmask, struct in_addr vhost,
                   const char *vhostname, const char *tftp_path,
                   const char *bootfile, struct in_addr vdhcp_start,
+                  struct in_addr vnext_server,
                   struct in_addr vnameserver, const char **vdnssearch,
                   void *opaque);
 void slirp_cleanup(Slirp *slirp);
diff --git a/slirp/slirp.c b/slirp/slirp.c
index 80b28ea..35f2afd 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -200,6 +200,7 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
                   struct in_addr vnetmask, struct in_addr vhost,
                   const char *vhostname, const char *tftp_path,
                   const char *bootfile, struct in_addr vdhcp_start,
+                  struct in_addr vnext_server,
                   struct in_addr vnameserver, const char **vdnssearch,
                   void *opaque)
 {
@@ -225,6 +226,7 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
     slirp->tftp_prefix = g_strdup(tftp_path);
     slirp->bootp_filename = g_strdup(bootfile);
     slirp->vdhcp_startaddr = vdhcp_start;
+    slirp->vnext_server = vnext_server;
     slirp->vnameserver_addr = vnameserver;
 
     if (vdnssearch) {
diff --git a/slirp/slirp.h b/slirp/slirp.h
index fe0e65d..a28a8d1 100644
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -209,6 +209,7 @@ struct Slirp {
     struct in_addr vnetwork_mask;
     struct in_addr vhost_addr;
     struct in_addr vdhcp_startaddr;
+    struct in_addr vnext_server;
     struct in_addr vnameserver_addr;
 
     struct in_addr client_ipaddr;
-- 
1.8.3.1