nspawn: add new --no-net switch to turn off networking in the container

3 files changed, 33 insertions, 7 deletions

diff --git a/Makefile.am b/Makefile.am
index 7971b6b774..c446527e1b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1341,7 +1341,8 @@ systemd_cgls_LDADD = \
 
 systemd_nspawn_SOURCES = \
 	src/nspawn.c \
-	src/cgroup-util.c
+	src/cgroup-util.c \
+        src/loopback-setup.c
 
 systemd_nspawn_CFLAGS = \
 	$(AM_CFLAGS)
diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 03c39fc3de..8b37519ad5 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -123,6 +123,7 @@
                 <variablelist>
                         <varlistentry>
                                 <term><option>--help</option></term>
+                                <term><option>-h</option></term>
 
                                 <listitem><para>Prints a short help
                                 text and exits.</para></listitem>
@@ -152,6 +153,16 @@
                                 </para></listitem>
                         </varlistentry>
 
+                        <varlistentry>
+                                <term><option>--no-net</option></term>
+
+                                <listitem><para>Turn off networking in
+                                the container. This makes all network
+                                interfaces unavailable in the
+                                container, with the exception of the
+                                loopback device.</para></listitem>
+                        </varlistentry>
+
                 </variablelist>
 
         </refsect1>
diff --git a/src/nspawn.c b/src/nspawn.c
index f4d63ea265..c97649d386 100644
--- a/src/nspawn.c
+++ b/src/nspawn.c
@@ -44,9 +44,11 @@
 #include "cgroup-util.h"
 #include "sd-daemon.h"
 #include "strv.h"
+#include "loopback-setup.h"
 
 static char *arg_directory = NULL;
 static char *arg_user = NULL;
+static bool arg_no_net = false;
 
 static int help(void) {
 
@@ -54,7 +56,8 @@ static int help(void) {
                "Spawn a minimal namespace container for debugging, testing and building.\n\n"
                "  -h --help            Show this help\n"
                "  -D --directory=NAME  Root directory for the container\n"
-               "  -u --user=USER       Run the command under specified user or uid\n",
+               "  -u --user=USER       Run the command under specified user or uid\n"
+               "     --no-net          Disable network  in container\n",
                program_invocation_short_name);
 
         return 0;
@@ -62,11 +65,16 @@ static int help(void) {
 
 static int parse_argv(int argc, char *argv[]) {
 
+        enum {
+                ARG_NO_NET = 0x100
+        };
+
         static const struct option options[] = {
-                { "help",      no_argument,       NULL, 'h' },
-                { "directory", required_argument, NULL, 'D' },
-                { "user",      optional_argument, NULL, 'u' },
-                { NULL,        0,                 NULL, 0   }
+                { "help",      no_argument,       NULL, 'h'        },
+                { "directory", required_argument, NULL, 'D'        },
+                { "user",      required_argument, NULL, 'u'        },
+                { "no-net",    no_argument,       NULL, ARG_NO_NET },
+                { NULL,        0,                 NULL, 0          }
         };
 
         int c;
@@ -100,6 +108,10 @@ static int parse_argv(int argc, char *argv[]) {
 
                         break;
 
+                case ARG_NO_NET:
+                        arg_no_net = true;
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -698,7 +710,7 @@ int main(int argc, char *argv[]) {
         sigset_add_many(&mask, SIGCHLD, SIGWINCH, SIGTERM, SIGINT, -1);
         assert_se(sigprocmask(SIG_BLOCK, &mask, NULL) == 0);
 
-        if ((pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS, NULL)) < 0) {
+        if ((pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS|(arg_no_net ? CLONE_NEWNET : 0), NULL)) < 0) {
                 log_error("clone() failed: %m");
                 goto finish;
         }
@@ -777,6 +789,8 @@ int main(int argc, char *argv[]) {
 
                 umask(0022);
 
+                loopback_setup();
+
                 if (drop_capabilities() < 0)
                         goto child_fail;