When not given an existing PID or network namspace to attach to, pasta
spawns a shell. Most commands which can spawn a shell in an altered
environment can also run other commands in that same environment, which can
be useful in automation.
Allow pasta to do the same thing; it can be given an arbitrary command to
run in the network and user namespace which pasta creates. If neither a
command nor an existing PID or netns to attach to is given, continue to
spawn a default shell, as before.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
conf.c | 27 ++++++++++++++++++---------
passt.1 | 14 +++++++++-----
pasta.c | 33 +++++++++++++++++++++++----------
pasta.h | 2 +-
4 files changed, 51 insertions(+), 25 deletions(-)
diff --git a/conf.c b/conf.c
index 2a18124..162c2dd 100644
--- a/conf.c
+++ b/conf.c
@@ -550,7 +550,8 @@ static int conf_ns_pid(char *userns, char *netns, const char *arg)
return 0;
}
- return -EINVAL;
+ /* Not a PID, later code will treat as a command */
+ return 0;
}
/**
@@ -1480,14 +1481,18 @@ void conf(struct ctx *c, int argc, char **argv)
check_root(c);
- if (c->mode == MODE_PASTA && optind + 1 == argc) {
- ret = conf_ns_pid(userns, netns, argv[optind]);
- if (ret < 0)
+ if (c->mode == MODE_PASTA) {
+ if (*netns && optind != argc) {
+ err("Both --netns and PID or command given");
usage(argv[0]);
- } else if (c->mode == MODE_PASTA && *userns
- && !*netns && optind == argc) {
- err("--userns requires --netns or PID");
- usage(argv[0]);
+ } else if (optind + 1 == argc) {
+ ret = conf_ns_pid(userns, netns, argv[optind]);
+ if (ret < 0)
+ usage(argv[0]);
+ } else if (*userns && !*netns && optind == argc) {
+ err("--userns requires --netns or PID");
+ usage(argv[0]);
+ }
} else if (optind != argc) {
usage(argv[0]);
}
@@ -1501,7 +1506,11 @@ void conf(struct ctx *c, int argc, char **argv)
if (ret < 0)
usage(argv[0]);
} else {
- pasta_start_ns(c);
+ if (*userns) {
+ err("Both --userns and command given");
+ usage(argv[0]);
+ }
+ pasta_start_ns(c, argc - optind, argv + optind);
}
}
diff --git a/passt.1 b/passt.1
index 4a09ced..3cc5a9d 100644
--- a/passt.1
+++ b/passt.1
@@ -15,7 +15,10 @@
[\fIOPTION\fR]...
.br
.B pasta
-[\fIOPTION\fR]... [\fIPID\fR]
+[\fIOPTION\fR]... [\fICOMMAND\fR [\fIARG\fR]...]
+.br
+.B pasta
+[\fIOPTION\fR]... \fIPID\fR
.br
.B pasta
[\fIOPTION\fR]... \fB--netns\fR [\fIPATH\fR|\fINAME\fR]
@@ -62,10 +65,11 @@ or with the \fBqrap\fR(1) wrapper.
equivalent functionality to network namespaces, as the one offered by
\fBpasst\fR for virtual machines.
-If PID or --netns are given, \fBpasta\fR associates to an existing user and
-network namespace. Otherwise, \fBpasta\fR creates a new user and network
-namespace, and spawns an interactive shell within this context. A \fItap\fR
-device within the network namespace is created to provide network connectivity.
+If PID or --netns are given, \fBpasta\fR associates to an existing
+user and network namespace. Otherwise, \fBpasta\fR creates a new user
+and network namespace, and spawns the given command or a default shell
+within this context. A \fItap\fR device within the network namespace
+is created to provide network connectivity.
For local TCP and UDP traffic only, \fBpasta\fR also implements a bypass path
directly mapping Layer-4 sockets between \fIinit\fR and target namespaces,
diff --git a/pasta.c b/pasta.c
index 830748f..a844af2 100644
--- a/pasta.c
+++ b/pasta.c
@@ -108,6 +108,7 @@ netns:
struct pasta_setup_ns_arg {
struct ctx *c;
int euid;
+ char **argv;
};
/**
@@ -119,7 +120,6 @@ struct pasta_setup_ns_arg {
static int pasta_setup_ns(void *arg)
{
struct pasta_setup_ns_arg *a = (struct pasta_setup_ns_arg *)arg;
- char *shell;
if (!a->c->netns_only) {
char buf[BUFSIZ];
@@ -139,29 +139,42 @@ static int pasta_setup_ns(void *arg)
FWRITE("/proc/sys/net/ipv4/ping_group_range", "0 0",
"Cannot set ping_group_range, ICMP requests might fail");
- shell = getenv("SHELL") ? getenv("SHELL") : "/bin/sh";
- if (strstr(shell, "/bash"))
- execve(shell, ((char *[]) { shell, "-l", NULL }), environ);
- else
- execve(shell, ((char *[]) { shell, NULL }), environ);
+ execvp(a->argv[0], a->argv);
- perror("execve");
+ perror("execvp");
exit(EXIT_FAILURE);
}
/**
- * pasta_start_ns() - Fork shell in new namespace if target ns is not given
+ * pasta_start_ns() - Fork command in new namespace if target ns is not given
* @c: Execution context
+ * @argc: Number of arguments for spawned command
+ * @argv: Command to spawn and arguments
*/
-void pasta_start_ns(struct ctx *c)
+void pasta_start_ns(struct ctx *c, int argc, char *argv[])
{
- struct pasta_setup_ns_arg arg = { .c = c, .euid = geteuid() };
+ struct pasta_setup_ns_arg arg = {
+ .c = c,
+ .euid = geteuid(),
+ .argv = argv,
+ };
+ char *shell = getenv("SHELL") ? getenv("SHELL") :
"/bin/sh";
+ char *sh_argv[] = { shell, NULL };
+ char *bash_argv[] = { shell, "-l", NULL };
char ns_fn_stack[NS_FN_STACK_SIZE];
c->foreground = 1;
if (!c->debug)
c->quiet = 1;
+ if (argc == 0) {
+ if (strstr(shell, "/bash")) {
+ arg.argv = bash_argv;
+ } else {
+ arg.argv = sh_argv;
+ }
+ }
+
pasta_child_pid = clone(pasta_setup_ns,
ns_fn_stack + sizeof(ns_fn_stack) / 2,
(c->netns_only ? 0 : CLONE_NEWNET) |
diff --git a/pasta.h b/pasta.h
index 8c80006..19b2e54 100644
--- a/pasta.h
+++ b/pasta.h
@@ -6,7 +6,7 @@
#ifndef PASTA_H
#define PASTA_H
-void pasta_start_ns(struct ctx *c);
+void pasta_start_ns(struct ctx *c, int argc, char *argv[]);
void pasta_ns_conf(struct ctx *c);
void pasta_child_handler(int signal);
int pasta_netns_quit_init(struct ctx *c);
--
2.37.2