[Devel] Re: [PATCH] user-cr: add --input-fd to take input from a specific fd

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at librato.com):
> This is useful if the user would like redirect the input from
> e.g, a socket or any other already open file descriptor when
> invoking 'restart'.
> 
> Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>

Acked-by: Serge Hallyn <serue at us.ibm.com>

> ---
>  restart.c |   34 +++++++++++++++++++++++++++-------
>  1 files changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/restart.c b/restart.c
> index 14d8aec..ca8e062 100644
> --- a/restart.c
> +++ b/restart.c
> @@ -72,7 +72,8 @@ static char usage_str[] =
>  "     --copy-status      imitate exit status of root task (implies -w)\n"
>  "  -W,--no-wait          do not wait for root task to terminate\n"
>  "  -F,--freezer=CGROUP   freeze tasks in freezer group CGROUP on success\n"
> -"  -i,--input=FILE      read data from FILE instead of standard input\n"
> +"  -i,--input=FILE       read data from FILE instead of standard input\n"
> +"     --input-fd=FD      read data from file descriptor FD (instead of stdin)\n"
>  "     --inspect          inspect image on-the-fly for error records\n"
>  "  -v,--verbose          verbose output\n"
>  "  -d,--debug            debugging output\n"
> @@ -353,6 +354,7 @@ struct args {
>  	int copy_status;
>  	char *freezer;
>  	char *input;
> +	int inputfd;
>  };
> 
>  static void usage(char *str)
> @@ -384,6 +386,7 @@ static void parse_args(struct args *args, int argc, char *argv[])
>  		{ "signal",	required_argument,	NULL, 4 },
>  		{ "inspect",	no_argument,		NULL, 5 },
>  		{ "input",	required_argument,	NULL, 'i' },
> +		{ "input-fd",	required_argument,	NULL, 7 },
>  		{ "root",	required_argument,	NULL, 'r' },
>  		{ "wait",	no_argument,		NULL, 'w' },
>  		{ "show-status",	no_argument,	NULL, 1 },
> @@ -401,6 +404,7 @@ static void parse_args(struct args *args, int argc, char *argv[])
>  	/* defaults */
>  	memset(args, 0, sizeof(*args));
>  	args->wait = 1;
> +	args->inputfd = -1;
> 
>  	while (1) {
>  		int c = getopt_long(argc, argv, optc, opts, NULL);
> @@ -420,6 +424,13 @@ static void parse_args(struct args *args, int argc, char *argv[])
>  		case 'i':
>  			args->input = optarg;
>  			break;
> +		case 7:
> +			args->inputfd = str2num(optarg);
> +			if (args->inputfd < 0) {
> +				printf("restart: invalid file descriptor\n");
> +				exit(1);
> +			}
> +			break;
>  		case 'p':
>  			args->pidns = 1;
>  			break;
> @@ -507,6 +518,11 @@ static void parse_args(struct args *args, int argc, char *argv[])
>  		printf("Invalid mix of --self with multiprocess options\n");
>  		exit(1);
>  	}
> +
> +	if (args->input && args->inputfd >= 0) {
> +		printf("Invalid used of both -i/--input and --input-fd\n");
> +		exit(1);
> +	}
>  }
> 
>  static void report_exit_status(int status, char *str, int debug)
> @@ -652,19 +668,23 @@ int main(int argc, char *argv[])
>  	parse_args(&args, argc, argv);
>  	ctx.args = &args;
> 
> -	/* input file (default: stdin) */
> +	/* input file ? */
>  	if (args.input) {
> -		ret = open(args.input, O_RDONLY, 0);
> -		if (ret < 0) {
> +		args.inputfd = open(args.input, O_RDONLY, 0);
> +		if (args.inputfd < 0) {
>  			perror("open input file");
>  			exit(1);
>  		}
> -		if (dup2(ret, STDIN_FILENO) < 0) {
> +	}
> +
> +	/* input file descriptor (default: stdin) */
> +	if (args.inputfd >= 0) {
> +		if (dup2(args.inputfd, STDIN_FILENO) < 0) {
>  			perror("dup2 input file");
>  			exit(1);
>  		}
> -		if (ret != STDIN_FILENO)
> -			close(ret);
> +		if (args.inputfd != STDIN_FILENO)
> +			close(args.inputfd);
>  	}
> 
>  	/* freezer preparation */
> -- 
> 1.6.0.4
> 
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