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[libvirt] [PATCH v2 2/4] net: support set public ip for forward mode nat



Support setting which public ip to use for NAT via attribute
address in subelement <nat> in <forward>:

...
  <forward mode='nat'>
      <nat address='1.2.3.4'/>
  </forward>
...

This will construct an iptables line using:

  '-j SNAT --to-source <address>'

instead of:

  '-j MASQUERADE'

Signed-off-by: Natanael Copa <ncopa alpinelinux org>
---
 docs/formatnetwork.html.in  |  13 ++++++
 src/conf/network_conf.c     | 100 +++++++++++++++++++++++++++++++++++++++++---
 src/conf/network_conf.h     |   3 ++
 src/network/bridge_driver.c |   8 ++++
 src/util/viriptables.c      |  45 +++++++++++++++-----
 src/util/viriptables.h      |   2 +
 6 files changed, 156 insertions(+), 15 deletions(-)

diff --git a/docs/formatnetwork.html.in b/docs/formatnetwork.html.in
index 7b42529..4ab1a75 100644
--- a/docs/formatnetwork.html.in
+++ b/docs/formatnetwork.html.in
@@ -136,6 +136,19 @@
             network, and to/from the host to the guests, are
             unrestricted and not NATed.<span class="since">Since
             0.4.2</span>
+
+            <p><span class="since">Since 1.0.3</span> it is possible to
+            specify the public IPv4 address to be used for the NAT by using
+            the <code>&lt;nat&gt;</code> subelement and attribute
+            <code>address</code>:
+            <pre>
+...
+  &lt;forward mode='nat'&gt;
+    &lt;nat address='1.2.3.4'/&gt;
+  &lt;/forward&gt;
+...
+            </pre>
+            </p>
           </dd>
 
           <dt><code>route</code></dt>
diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index c93916d..a9aa139 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -1325,6 +1325,43 @@ cleanup:
 }
 
 static int
+virNetworkForwardNatDefParseXML(const char *networkName,
+                                xmlNodePtr node,
+                                xmlXPathContextPtr ctxt,
+                                virNetworkForwardDefPtr def)
+{
+    int ret = -1;
+    char *addr_start = NULL;
+    xmlNodePtr save = ctxt->node;
+
+    ctxt->node = node;
+
+    if (def->type != VIR_NETWORK_FORWARD_NAT) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("The <nat> element can only be used when <forward> 'mode' is 'nat' in network %s"),
+                       networkName);
+        goto cleanup;
+    }
+
+    /* addresses for SNAT */
+    addr_start = virXPathString("string(./@address)", ctxt);
+
+    if (addr_start && virSocketAddrParse(&def->addr_start, addr_start, AF_INET) < 0) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("Bad ipv4 address '%s' in <nat> in <forward> in "
+                         "network '%s'"), addr_start, networkName);
+        goto cleanup;
+    }
+
+    ret = 0;
+
+cleanup:
+    VIR_FREE(addr_start);
+    ctxt->node = save;
+    return ret;
+}
+
+static int
 virNetworkForwardDefParseXML(const char *networkName,
                              xmlNodePtr node,
                              xmlXPathContextPtr ctxt,
@@ -1334,7 +1371,8 @@ virNetworkForwardDefParseXML(const char *networkName,
     xmlNodePtr *forwardIfNodes = NULL;
     xmlNodePtr *forwardPfNodes = NULL;
     xmlNodePtr *forwardAddrNodes = NULL;
-    int nForwardIfs, nForwardAddrs, nForwardPfs;
+    xmlNodePtr *forwardNatNodes = NULL;
+    int nForwardIfs, nForwardAddrs, nForwardPfs, nForwardNats;
     char *forwardDev = NULL;
     char *forwardManaged = NULL;
     char *type = NULL;
@@ -1384,6 +1422,24 @@ virNetworkForwardDefParseXML(const char *networkName,
         goto cleanup;
     }
 
+    nForwardNats = virXPathNodeSet("./nat", ctxt, &forwardNatNodes);
+    if (nForwardNats < 0) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("invalid <nat> element found in <forward> of network %s"),
+                       networkName);
+        goto cleanup;
+    } else if (nForwardNats > 1) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("Only one <nat> element is allowed in <forward> of network %s"),
+                       networkName);
+        goto cleanup;
+    } else if (nForwardNats == 1) {
+        if (virNetworkForwardNatDefParseXML(networkName,
+                                            *forwardNatNodes,
+                                            ctxt, def) < 0)
+            goto cleanup;
+    }
+
     if (((nForwardIfs > 0) + (nForwardAddrs > 0) + (nForwardPfs > 0)) > 1) {
         virReportError(VIR_ERR_XML_ERROR,
                        _("<address>, <interface>, and <pf> elements in <forward> "
@@ -1525,6 +1581,7 @@ cleanup:
     VIR_FREE(forwardPfNodes);
     VIR_FREE(forwardIfNodes);
     VIR_FREE(forwardAddrNodes);
+    VIR_FREE(forwardNatNodes);
     ctxt->node = save;
     return ret;
 }
@@ -2078,13 +2135,40 @@ virPortGroupDefFormat(virBufferPtr buf,
 }
 
 static int
+virNatDefFormat(virBufferPtr buf,
+                const virNetworkForwardDefPtr fwd)
+{
+    char *addr_start = NULL;
+    int ret = -1;
+
+    if (VIR_SOCKET_ADDR_VALID(&fwd->addr_start)) {
+        addr_start = virSocketAddrFormat(&fwd->addr_start);
+        if (!addr_start)
+            goto cleanup;
+    }
+
+    if (!addr_start)
+        return 0;
+
+    virBufferAddLit(buf, "<nat");
+    virBufferAsprintf(buf, " address='%s'", addr_start);
+    virBufferAsprintf(buf, "/>\n");
+
+    ret = 0;
+
+cleanup:
+    VIR_FREE(addr_start);
+    return ret;
+}
+
+static int
 virNetworkDefFormatInternal(virBufferPtr buf,
                             const virNetworkDefPtr def,
                             unsigned int flags)
 {
     unsigned char *uuid;
     char uuidstr[VIR_UUID_STRING_BUFLEN];
-    int ii;
+    int ii, shortforward;
 
     virBufferAddLit(buf, "<network");
     if (!(flags & VIR_NETWORK_XML_INACTIVE) && (def->connections > 0)) {
@@ -2121,10 +2205,16 @@ virNetworkDefFormatInternal(virBufferPtr buf,
             else
                 virBufferAddLit(buf, " managed='no'");
         }
-        virBufferAsprintf(buf, "%s>\n",
-                          (def->forward.nifs || def->forward.npfs) ? "" : "/");
+        shortforward = !(def->forward.nifs || def->forward.npfs
+                         || VIR_SOCKET_ADDR_VALID(&def->forward.addr_start));
+        virBufferAsprintf(buf, "%s>\n", shortforward ? "/" : "");
         virBufferAdjustIndent(buf, 2);
 
+        if (def->forward.type == VIR_NETWORK_FORWARD_NAT) {
+            if (virNatDefFormat(buf, &def->forward) < 0)
+                goto error;
+        }
+
         /* For now, hard-coded to at most 1 forward.pfs */
         if (def->forward.npfs)
             virBufferEscapeString(buf, "<pf dev='%s'/>\n",
@@ -2154,7 +2244,7 @@ virNetworkDefFormatInternal(virBufferPtr buf,
             }
         }
         virBufferAdjustIndent(buf, -2);
-        if (def->forward.npfs || def->forward.nifs)
+        if (!shortforward)
             virBufferAddLit(buf, "</forward>\n");
     }
 
diff --git a/src/conf/network_conf.h b/src/conf/network_conf.h
index 4c634ed..4a5ce92 100644
--- a/src/conf/network_conf.h
+++ b/src/conf/network_conf.h
@@ -174,6 +174,9 @@ struct _virNetworkForwardDef {
 
     size_t nifs;
     virNetworkForwardIfDefPtr ifs;
+
+    /* adress for SNAT */
+    virSocketAddr addr_start;
 };
 
 typedef struct _virPortGroupDef virPortGroupDef;
diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 21255f0..05ef19c 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -1590,6 +1590,7 @@ networkAddMasqueradingIptablesRules(struct network_driver *driver,
                                      &ipdef->address,
                                      prefix,
                                      forwardIf,
+                                     &network->def->forward.addr_start,
                                      NULL) < 0) {
         virReportError(VIR_ERR_SYSTEM_ERROR,
                        forwardIf ?
@@ -1604,6 +1605,7 @@ networkAddMasqueradingIptablesRules(struct network_driver *driver,
                                      &ipdef->address,
                                      prefix,
                                      forwardIf,
+                                     &network->def->forward.addr_start,
                                      "udp") < 0) {
         virReportError(VIR_ERR_SYSTEM_ERROR,
                        forwardIf ?
@@ -1618,6 +1620,7 @@ networkAddMasqueradingIptablesRules(struct network_driver *driver,
                                      &ipdef->address,
                                      prefix,
                                      forwardIf,
+                                     &network->def->forward.addr_start,
                                      "tcp") < 0) {
         virReportError(VIR_ERR_SYSTEM_ERROR,
                        forwardIf ?
@@ -1634,12 +1637,14 @@ networkAddMasqueradingIptablesRules(struct network_driver *driver,
                                     &ipdef->address,
                                     prefix,
                                     forwardIf,
+                                    &network->def->forward.addr_start,
                                     "udp");
  masqerr4:
     iptablesRemoveForwardMasquerade(driver->iptables,
                                     &ipdef->address,
                                     prefix,
                                     forwardIf,
+                                    &network->def->forward.addr_start,
                                     NULL);
  masqerr3:
     iptablesRemoveForwardAllowRelatedIn(driver->iptables,
@@ -1670,16 +1675,19 @@ networkRemoveMasqueradingIptablesRules(struct network_driver *driver,
                                         &ipdef->address,
                                         prefix,
                                         forwardIf,
+                                        &network->def->forward.addr_start,
                                         "tcp");
         iptablesRemoveForwardMasquerade(driver->iptables,
                                         &ipdef->address,
                                         prefix,
                                         forwardIf,
+                                        &network->def->forward.addr_start,
                                         "udp");
         iptablesRemoveForwardMasquerade(driver->iptables,
                                         &ipdef->address,
                                         prefix,
                                         forwardIf,
+                                        &network->def->forward.addr_start,
                                         NULL);
 
         iptablesRemoveForwardAllowRelatedIn(driver->iptables,
diff --git a/src/util/viriptables.c b/src/util/viriptables.c
index b03b0e9..12d1b2e 100644
--- a/src/util/viriptables.c
+++ b/src/util/viriptables.c
@@ -397,7 +397,7 @@ iptablesForwardAllowOut(iptablesContext *ctx,
                              action);
     virCommandAddArgList(cmd,
                          "--source", networkstr,
-			 "--in-interface", iface, NULL);
+                         "--in-interface", iface, NULL);
 
     if (physdev && physdev[0])
         virCommandAddArgList(cmd, "--out-interface", physdev, NULL);
@@ -805,11 +805,13 @@ iptablesForwardMasquerade(iptablesContext *ctx,
                           virSocketAddr *netaddr,
                           unsigned int prefix,
                           const char *physdev,
+                          virSocketAddr *addr_start,
                           const char *protocol,
                           int action)
 {
-    int ret;
-    char *networkstr;
+    int ret = -1;
+    char *networkstr = NULL;
+    char *addr_start_str = NULL;
     virCommandPtr cmd = NULL;
 
     if (!(networkstr = iptablesFormatNetwork(netaddr, prefix)))
@@ -820,8 +822,13 @@ iptablesForwardMasquerade(iptablesContext *ctx,
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        _("Attempted to NAT '%s'. NAT is only supported for IPv4."),
                        networkstr);
-        VIR_FREE(networkstr);
-        return -1;
+        goto cleanup;
+    }
+
+    if (VIR_SOCKET_ADDR_IS_FAMILY(addr_start, AF_INET)) {
+        addr_start_str = virSocketAddrFormat(addr_start);
+        if (!addr_start_str)
+            goto cleanup;
     }
 
     cmd = iptablesCommandNew(ctx->nat_postrouting, AF_INET, action);
@@ -835,12 +842,28 @@ iptablesForwardMasquerade(iptablesContext *ctx,
     if (physdev && physdev[0])
         virCommandAddArgList(cmd, "--out-interface", physdev, NULL);
 
-    virCommandAddArgList(cmd, "--jump", "MASQUERADE", NULL);
+    /* Use --jump SNAT if public addr is specified */
+    if (addr_start_str && addr_start_str[0]) {
+        char tmpstr[sizeof("123.123.123.123-123.123.123.123:65535-65535")];
+        const char *portstr = "";
 
-    if (protocol && protocol[0])
-        virCommandAddArgList(cmd, "--to-ports", "1024-65535", NULL);
+        memset(tmpstr, 0, sizeof(tmpstr));
+        if (protocol && protocol[0])
+            portstr = ":1024-65535";
+
+        snprintf(tmpstr, sizeof(tmpstr), "%s%s", addr_start_str, portstr);
+
+        virCommandAddArgList(cmd, "--jump", "SNAT",
+                                  "--to-source", tmpstr, NULL);
+     } else {
+         virCommandAddArgList(cmd, "--jump", "MASQUERADE", NULL);
+
+         if (protocol && protocol[0])
+             virCommandAddArgList(cmd, "--to-ports", "1024-65535", NULL);
+     }
 
     ret = iptablesCommandRunAndFree(cmd);
+cleanup:
     VIR_FREE(networkstr);
     return ret;
 }
@@ -863,9 +886,10 @@ iptablesAddForwardMasquerade(iptablesContext *ctx,
                              virSocketAddr *netaddr,
                              unsigned int prefix,
                              const char *physdev,
+                             virSocketAddr *addr_start,
                              const char *protocol)
 {
-    return iptablesForwardMasquerade(ctx, netaddr, prefix, physdev, protocol, ADD);
+    return iptablesForwardMasquerade(ctx, netaddr, prefix, physdev, addr_start, protocol, ADD);
 }
 
 /**
@@ -886,9 +910,10 @@ iptablesRemoveForwardMasquerade(iptablesContext *ctx,
                                 virSocketAddr *netaddr,
                                 unsigned int prefix,
                                 const char *physdev,
+                                virSocketAddr *addr_start,
                                 const char *protocol)
 {
-    return iptablesForwardMasquerade(ctx, netaddr, prefix, physdev, protocol, REMOVE);
+    return iptablesForwardMasquerade(ctx, netaddr, prefix, physdev, addr_start, protocol, REMOVE);
 }
 
 
diff --git a/src/util/viriptables.h b/src/util/viriptables.h
index d7fa731..b75a5ea 100644
--- a/src/util/viriptables.h
+++ b/src/util/viriptables.h
@@ -107,11 +107,13 @@ int              iptablesAddForwardMasquerade    (iptablesContext *ctx,
                                                   virSocketAddr *netaddr,
                                                   unsigned int prefix,
                                                   const char *physdev,
+                                                  virSocketAddr *addr_start,
                                                   const char *protocol);
 int              iptablesRemoveForwardMasquerade (iptablesContext *ctx,
                                                   virSocketAddr *netaddr,
                                                   unsigned int prefix,
                                                   const char *physdev,
+                                                  virSocketAddr *addr_start,
                                                   const char *protocol);
 int              iptablesAddOutputFixUdpChecksum (iptablesContext *ctx,
                                                   const char *iface,
-- 
1.8.1.2


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