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Date: Wed, 5 Apr 2023 13:58:00 +0200
From: Stefano Brivio <sbrivio@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH 04/14] nstool: Split some command line parsing and
socket setup to subcommands
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On Tue, 4 Apr 2023 11:46:28 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:
> This will make it easier to differentiate the options to those commands
> further in future.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
> test/nstool.c | 102 +++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 68 insertions(+), 34 deletions(-)
>
> diff --git a/test/nstool.c b/test/nstool.c
> index 7e069b6..9ea7eeb 100644
> --- a/test/nstool.c
> +++ b/test/nstool.c
> @@ -11,6 +11,7 @@
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> +#include <stdbool.h>
> #include <errno.h>
> #include <unistd.h>
> #include <sys/socket.h>
> @@ -37,19 +38,55 @@ static void usage(void)
> " terminate.\n");
> }
>
> -static void hold(int fd, const struct sockaddr_un *addr)
> +static int connect_ctl(const char * sockpath, bool wait)
> {
> + int fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
> + struct sockaddr_un addr = {
> + .sun_family = AF_UNIX,
> + };
> int rc;
>
> - rc = bind(fd, (struct sockaddr *)addr, sizeof(*addr));
> + if (fd < 0)
> + die("socket(): %s\n", strerror(errno));
Unrelated: it would be nice if die() added newlines eventually.
> +
> + strncpy(addr.sun_path, sockpath, UNIX_PATH_MAX);
> +
> + do {
> + rc = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
> + if (rc < 0 &&
> + (!wait || (errno != ENOENT && errno != ECONNREFUSED)))
> + die("connect() to %s: %s\n", sockpath, strerror(errno));
A (1ms?) delay would be nice to have here -- it's almost a busyloop,
connect() fails fast.
> + } while (rc < 0);
> +
> + return fd;
> +}
> +
> +static void cmd_hold(int argc, char *argv[])
> +{
> + int fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
> + struct sockaddr_un addr = {
> + .sun_family = AF_UNIX,
> + };
> + const char *sockpath = argv[1];
> + int rc;
> +
> + if (argc != 2)
> + usage();
> +
> + if (fd < 0)
> + die("socket(): %s\n", strerror(errno));
> +
> + strncpy(addr.sun_path, sockpath, UNIX_PATH_MAX);
> +
> + rc = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
> if (rc < 0)
> - die("bind(): %s\n", strerror(errno));
> + die("bind() to %s: %s\n", sockpath, strerror(errno));
>
> rc = listen(fd, 0);
> if (rc < 0)
> - die("listen(): %s\n", strerror(errno));
> + die("listen() on %s: %s\n", sockpath, strerror(errno));
>
> - printf("nstool: local PID=%d local UID=%u local GID=%u\n",
> + printf("nstool hold: local PID=%d local UID=%u local GID=%u\n",
> getpid(), getuid(), getgid());
> do {
> int afd = accept(fd, NULL, NULL);
> @@ -63,71 +100,68 @@ static void hold(int fd, const struct sockaddr_un *addr)
> die("read(): %s\n", strerror(errno));
> } while (rc == 0);
>
> - unlink(addr->sun_path);
> + unlink(sockpath);
> }
>
> -static void pid(int fd, const struct sockaddr_un *addr)
> +static void cmd_pid(int argc, char *argv[])
> {
> - int rc;
> + const char *sockpath = argv[1];
> struct ucred peercred;
> socklen_t optlen = sizeof(peercred);
> + int fd, rc;
>
> - do {
> - rc = connect(fd, (struct sockaddr *)addr, sizeof(*addr));
> - if (rc < 0 && errno != ENOENT && errno != ECONNREFUSED)
> - die("connect(): %s\n", strerror(errno));
> - } while (rc < 0);
> + if (argc != 2)
> + usage();
> +
> + fd = connect_ctl(sockpath, true);
I didn't spot this earlier, but... does it really make sense to wait in
cmd_pid(), also on ENOENT, rather than making 'hold' return only once
the socket is ready? I don't think it would be outrageous to have
'nstool pid' failing if the holding process doesn't exist.
Admittely, I'm biased by the few hundreds of times I needed to
'killall -9 nsholder' in the past months. :)
>
> rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED,
> &peercred, &optlen);
> if (rc < 0)
> - die("getsockopet(SO_PEERCRED): %s\n", strerror(errno));
> + die("getsockopet(SO_PEERCRED) %s: %s\n",
> + sockpath, strerror(errno));
>
> close(fd);
>
> printf("%d\n", peercred.pid);
> }
>
> -static void stop(int fd, const struct sockaddr_un *addr)
> +static void cmd_stop(int argc, char *argv[])
> {
> - int rc;
> + const char *sockpath = argv[1];
> + int fd, rc;
> char buf = 'Q';
>
> - rc = connect(fd, (struct sockaddr *)addr, sizeof(*addr));
> - if (rc < 0)
> - die("connect(): %s\n", strerror(errno));
> + if (argc != 2)
> + usage();
> +
> + fd = connect_ctl(sockpath, false);
>
> rc = write(fd, &buf, sizeof(buf));
Unrelated: a compound literal would make this more readable.
--
Stefano