Node: support setHostname to run a node in its own UTS namespace

mininet/node.py

@@ -74,9 +74,10 @@ class Node( object ):
 
     portBase = 0  # Nodes always start with eth0/port0, even in OF 1.0
 
-    def __init__( self, name, inNamespace=True, **params ):
+    def __init__( self, name, inNamespace=True, setHostname=False, **params ):
         """name: name of node
            inNamespace: in network namespace?
+           setHostname: in uts namespace?
            privateDirs: list of private directory strings or tuples
            params: Node parameters (see config() for details)"""
 
@@ -86,6 +87,7 @@ def __init__( self, name, inNamespace=True, **params ):
         self.name = params.get( 'name', name )
         self.privateDirs = params.get( 'privateDirs', [] )
         self.inNamespace = params.get( 'inNamespace', inNamespace )
+        self.setHostname = params.get( 'setHostname', setHostname )
 
         # Stash configuration parameters for future reference
         self.params = params
@@ -127,15 +129,19 @@ def startShell( self, mnopts=None ):
             error( "%s: shell is already running\n" % self.name )
             return
         # mnexec: (c)lose descriptors, (d)etach from tty,
-        # (p)rint pid, and run in (n)amespace
-        opts = '-cd' if mnopts is None else mnopts
+        # (p)rint pid, run in (n)amespace, unshare (u)ts with a hostname
+        mnexec = ['mnexec']
+        mnexec.append('-cd' if not mnopts else mnopts)
         if self.inNamespace:
-            opts += 'n'
+            mnexec.append('-n')
+        if self.setHostname:
+            mnexec.extend(['-u', self.name])
         # bash -i: force interactive
         # -s: pass $* to shell, and make process easy to find in ps
         # prompt is set to sentinel chr( 127 )
-        cmd = [ 'mnexec', opts, 'env', 'PS1=' + chr( 127 ),
-                'bash', '--norc', '-is', 'mininet:' + self.name ]
+        bash = [ 'env', 'PS1=' + chr( 127 ),
+                 'bash', '--norc', '-is', 'mininet:' + self.name ]
+        cmd = mnexec + bash
         # Spawn a shell subprocess in a pseudo-tty, to disable buffering
         # in the subprocess and insulate it from signals (e.g. SIGINT)
         # received by the parent

mininet/topolib.py

@@ -34,6 +34,7 @@ def addTree( self, depth, fanout ):
 
 def TreeNet( depth=1, fanout=2, **kwargs ):
     "Convenience function for creating tree networks."
+    # topo = TreeTopo( depth, fanout, hopts={'setHostname':True})
     topo = TreeTopo( depth, fanout )
     return Mininet( topo, **kwargs )
 

mnexec.c

@@ -15,6 +15,7 @@
 
 #define _GNU_SOURCE
 #include <stdio.h>
+#include <string.h>
 #include <linux/sched.h>
 #include <unistd.h>
 #include <limits.h>
@@ -32,15 +33,16 @@
 void usage(char *name)
 {
     printf("Execution utility for Mininet\n\n"
-           "Usage: %s [-cdnp] [-a pid] [-g group] [-r rtprio] cmd args...\n\n"
+           "Usage: %s [-cdnp] [-a pid] [-g group] [-r rtprio] [-u hostname] cmd args...\n\n"
            "Options:\n"
            "  -c: close all file descriptors except stdin/out/error\n"
            "  -d: detach from tty by calling setsid()\n"
            "  -n: run in new network and mount namespaces\n"
            "  -p: print ^A + pid\n"
-           "  -a pid: attach to pid's network and mount namespaces\n"
+           "  -a pid: attach to pid's network, mount and UTS namespaces\n"
            "  -g group: add to cgroup\n"
            "  -r rtprio: run with SCHED_RR (usually requires -g)\n"
+           "  -u hostname: run in new uts namespace\n"
            "  -v: print version\n",
            name);
 }
@@ -102,7 +104,7 @@ int main(int argc, char *argv[])
     char *cwd = get_current_dir_name();
 
     static struct sched_param sp;
-    while ((c = getopt(argc, argv, "+cdnpa:g:r:vh")) != -1)
+    while ((c = getopt(argc, argv, "+cdnpa:g:r:u:vh")) != -1)
         switch(c) {
         case 'c':
             /* close file descriptors except stdin/out/error */
@@ -154,7 +156,7 @@ int main(int argc, char *argv[])
         case 'a':
             /* Attach to pid's network namespace and mount namespace */
             pid = atoi(optarg);
-            sprintf(path, "/proc/%d/ns/net", pid);
+            snprintf(path, PATH_MAX, "/proc/%d/ns/net", pid);
             nsid = open(path, O_RDONLY);
             if (nsid < 0) {
                 perror(path);
@@ -165,11 +167,11 @@ int main(int argc, char *argv[])
                 return 1;
             }
             /* Plan A: call setns() to attach to mount namespace */
-            sprintf(path, "/proc/%d/ns/mnt", pid);
+            snprintf(path, PATH_MAX, "/proc/%d/ns/mnt", pid);
             nsid = open(path, O_RDONLY);
             if (nsid < 0 || setns(nsid, 0) != 0) {
                 /* Plan B: chroot/chdir into pid's root file system */
-                sprintf(path, "/proc/%d/root", pid);
+                snprintf(path, PATH_MAX, "/proc/%d/root", pid);
                 if (chroot(path) < 0) {
                     perror(path);
                     return 1;
@@ -180,6 +182,17 @@ int main(int argc, char *argv[])
                 perror(cwd);
                 return 1;
             }
+            /* Attach to pid's UTS namespace */
+            snprintf(path, PATH_MAX, "/proc/%d/ns/uts", pid);
+            nsid = open(path, O_RDONLY);
+            if (nsid < 0) {
+                perror(path);
+                return 1;
+            }
+            if (setns(nsid, 0) != 0) {
+                perror("setns");
+                return 1;
+            }
             break;
         case 'g':
             /* Attach to cgroup */
@@ -193,6 +206,16 @@ int main(int argc, char *argv[])
                 return 1;
             }
             break;
+        case 'u':
+            if (unshare(CLONE_NEWUTS) == -1) {
+                perror("unshare NEWUTS");
+                return 1;
+            }
+            if (sethostname(optarg, strlen(optarg)) == -1) {
+                perror("sethostname");
+                return 1;
+            }
+            break;
         case 'v':
             printf("%s\n", VERSION);
             exit(0);