Re: [PATCH 04/14] nstool: Split some command line parsing and socket setup to subcommands

[Stefano Brivio <sbrivio@redhat.com>]

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