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Date: Wed, 5 Apr 2023 13:58:54 +0200
From: Stefano Brivio <sbrivio@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH 09/14] nstool: Add nstool exec command to execute
commands in an nstool namespace
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On Tue, 4 Apr 2023 11:46:33 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:
> This combines nstool info -pw <sock> with nsenter with various options for
> a more convenient and less verbose of entering existing nstool managed
> namespaces.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
> test/nstool.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 137 insertions(+), 2 deletions(-)
>
> diff --git a/test/nstool.c b/test/nstool.c
> index 5681ce8..25079aa 100644
> --- a/test/nstool.c
> +++ b/test/nstool.c
> @@ -17,7 +17,9 @@
> #include <unistd.h>
> #include <getopt.h>
> #include <stdarg.h>
> +#include <fcntl.h>
> #include <sys/socket.h>
> +#include <sys/wait.h>
> #include <linux/un.h>
> #include <linux/limits.h>
> #include <sched.h>
> @@ -75,6 +77,9 @@ static void usage(void)
> " socket at SOCK\n"
> " -p Print just the holder's PID as seen by the caller\n"
> " -w Retry connecting to SOCK until it is ready\n"
> + " nstool exec SOCK [COMMAND [ARGS...]]\n"
> + " Execute command or shell in the namespaces of the nstool hold\n"
> + " with control socket at SOCK\n"
> " nstool stop SOCK\n"
> " Instruct the nstool hold with control socket at SOCK to\n"
> " terminate.\n");
> @@ -84,7 +89,7 @@ static int connect_ctl(const char *sockpath, bool wait,
> struct holder_info *info,
> struct ucred *peercred)
> {
> - int fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
> + int fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, PF_UNIX);
> struct sockaddr_un addr = {
> .sun_family = AF_UNIX,
> };
> @@ -132,7 +137,7 @@ static int connect_ctl(const char *sockpath, bool wait,
>
> static void cmd_hold(int argc, char *argv[])
> {
> - int fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
> + int fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, PF_UNIX);
> struct sockaddr_un addr = {
> .sun_family = AF_UNIX,
> };
> @@ -301,6 +306,134 @@ static void cmd_info(int argc, char *argv[])
> }
> }
>
> +static int openns(const char *fmt, ...)
> +{
> + char nspath[PATH_MAX];
> + va_list ap;
> + int fd;
> +
> + va_start(ap, fmt);
> + if (vsnprintf(nspath, sizeof(nspath), fmt, ap) >= PATH_MAX)
> + die("Truncated path \"%s\"\n", nspath);
> + va_end(ap);
> +
> + fd = open(nspath, O_RDONLY | O_CLOEXEC);
> + if (fd < 0)
> + die("open() %s: %s\n", nspath, strerror(errno));
> +
> + return fd;
> +}
> +
> +static void wait_for_child(pid_t pid)
> +{
> + int status;
> +
> + /* Match the child's exit status, if possible */
> + for (;;) {
> + pid_t rc;
> +
> + rc = waitpid(pid, &status, WUNTRACED);
> + if (rc < 0)
> + die("waitpid() on %d: %s\n", pid, strerror(errno));
> + if (rc != pid)
> + die("waitpid() on %d returned %d", pid, rc);
> + if (WIFSTOPPED(status)) {
> + /* Stop the parent to patch */
> + kill(getpid(), SIGSTOP);
> + /* We must have resumed, resume the child */
> + kill(pid, SIGCONT);
> + continue;
> + }
> +
> + break;
> + }
> +
> + if (WIFEXITED(status))
> + exit(WEXITSTATUS(status));
> + else if (WIFSIGNALED(status))
> + kill(getpid(), WTERMSIG(status));
An alternative could be what pasta_child_handler() does on
WIFSIGNALED(status) -- I don't actually have a preference between the
two.
> +
> + die("Unexpected status for child %d\n", pid);
Weird indentation in this function.
--
Stefano