Re: [PATCH rfc 2/2] fabrics: allow user to pass hostname instead of traddr

[Keith Busch <kbusch@kernel.org>]

On Tue, Mar 24, 2020 at 02:03:24AM -0700, Sagi Grimberg wrote:
> Some users would like to use well known hostnames instead
> of remembering ip addresses. So, allow users to pass --hostname
> and we will attempt to resolve against the DNS.
> 
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>  fabrics.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 75 insertions(+)
> 
> diff --git a/fabrics.c b/fabrics.c
> index a7d628b1f0c9..7bd95c4b0d10 100644
> --- a/fabrics.c
> +++ b/fabrics.c
> @@ -33,6 +33,10 @@
>  #include <sys/stat.h>
>  #include <stddef.h>
>  
> +#include <sys/types.h>
> +#include <arpa/inet.h>
> +#include <netdb.h>
> +
>  #include "util/parser.h"
>  #include "nvme-ioctl.h"
>  #include "nvme-status.h"
> @@ -60,6 +64,7 @@ static struct config {
>  	char *nqn;
>  	char *transport;
>  	char *traddr;
> +	char *hostname;
>  	char *trsvcid;
>  	char *host_traddr;
>  	char *hostnqn;
> @@ -857,6 +862,54 @@ static int build_options(char *argstr, int max_len, bool discover)
>  	return 0;
>  }

The code looks fine.

I realize 'hostname' in this context is referring to the remote host and
resolves the target's transport address, but it just sounds potentially
confusing given we have "host_traddr". I'm not sure of a better name,
though, so if this is normal convention, then okay.
  
> +static int hostname2traddr(struct config *cfg)
> +{
> +	struct addrinfo *host_info, hints = {.ai_family = AF_UNSPEC};
> +	char addrstr[NVMF_TRADDR_SIZE];
> +	const char *p;
> +	int ret;
> +
> +	if (cfg->traddr) {
> +		fprintf(stderr, "hostname and traddr cannot be passed together\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = getaddrinfo(cfg->hostname, NULL, &hints, &host_info);
> +	if (ret) {
> +		fprintf(stderr, "failed to get host info for %s\n", cfg->hostname);
> +		return ret;
> +	}
> +
> +	switch (host_info->ai_family) {
> +	case AF_INET:
> +		p = inet_ntop(host_info->ai_family,
> +			&(((struct sockaddr_in *)host_info->ai_addr)->sin_addr),
> +			addrstr, NVMF_TRADDR_SIZE);
> +		break;
> +	case AF_INET6:
> +		p = inet_ntop(host_info->ai_family,
> +			&(((struct sockaddr_in6 *)host_info->ai_addr)->sin6_addr),
> +			addrstr, NVMF_TRADDR_SIZE);
> +		break;
> +	default:
> +		fprintf(stderr, "unrecognized address family (%d) %s\n",
> +			host_info->ai_family, cfg->hostname);
> +		ret = -EINVAL;
> +		goto free_addrinfo;
> +	}
> +
> +	if (!p) {
> +		fprintf(stderr, "failed to get traddr for %s\n", cfg->hostname);
> +		ret = -errno;
> +		goto free_addrinfo;
> +	}
> +	cfg->traddr = strdup(addrstr);
> +
> +free_addrinfo:
> +	freeaddrinfo(host_info);
> +	return ret;
> +}
> +
>  static int connect_ctrl(struct nvmf_disc_rsp_page_entry *e)
>  {
>  	char argstr[BUF_SIZE], *p;
> @@ -1230,6 +1283,13 @@ static int discover_from_conf_file(const char *desc, char *argstr,
>  		if (cfg.persistent && !cfg.keep_alive_tmo)
>  			cfg.keep_alive_tmo = NVMF_DEF_DISC_TMO;
>  
> +		if (cfg.hostname) {
> +			ret = hostname2traddr(&cfg);
> +			if (ret)
> +				goto out;
> +			cfg.hostname = NULL;
> +		}
> +
>  		err = build_options(argstr, BUF_SIZE, true);
>  		if (err) {
>  			ret = err;
> @@ -1259,6 +1319,7 @@ int fabrics_discover(const char *desc, int argc, char **argv, bool connect)
>  	OPT_ARGS(opts) = {
>  		OPT_LIST("transport",      't', &cfg.transport,       "transport type"),
>  		OPT_LIST("traddr",         'a', &cfg.traddr,          "transport address"),
> +		OPT_LIST("hostname",       'A', &cfg.hostname,        "transport address in a hostname form"),
>  		OPT_LIST("trsvcid",        's', &cfg.trsvcid,         "transport service id (e.g. IP port)"),
>  		OPT_LIST("host-traddr",    'w', &cfg.host_traddr,     "host traddr (e.g. FC WWN's)"),
>  		OPT_LIST("hostnqn",        'q', &cfg.hostnqn,         "user-defined hostnqn (if default not used)"),
> @@ -1295,6 +1356,13 @@ int fabrics_discover(const char *desc, int argc, char **argv, bool connect)
>  	} else {
>  		if (cfg.persistent && !cfg.keep_alive_tmo)
>  			cfg.keep_alive_tmo = NVMF_DEF_DISC_TMO;
> +
> +		if (cfg.hostname) {
> +			ret = hostname2traddr(&cfg);
> +			if (ret)
> +				goto out;
> +		}
> +
>  		ret = build_options(argstr, BUF_SIZE, true);
>  		if (ret)
>  			goto out;
> @@ -1315,6 +1383,7 @@ int fabrics_connect(const char *desc, int argc, char **argv)
>  		OPT_LIST("transport",         't', &cfg.transport,         "transport type"),
>  		OPT_LIST("nqn",               'n', &cfg.nqn,               "nqn name"),
>  		OPT_LIST("traddr",            'a', &cfg.traddr,            "transport address"),
> +		OPT_LIST("hostname",          'A', &cfg.hostname,          "transport address in a hostname form"),
>  		OPT_LIST("trsvcid",           's', &cfg.trsvcid,           "transport service id (e.g. IP port)"),
>  		OPT_LIST("host-traddr",       'w', &cfg.host_traddr,       "host traddr (e.g. FC WWN's)"),
>  		OPT_LIST("hostnqn",           'q', &cfg.hostnqn,           "user-defined hostnqn"),
> @@ -1339,6 +1408,12 @@ int fabrics_connect(const char *desc, int argc, char **argv)
>  	if (ret)
>  		goto out;
>  
> +	if (cfg.hostname) {
> +		ret = hostname2traddr(&cfg);
> +		if (ret)
> +			goto out;
> +	}
> +
>  	ret = build_options(argstr, BUF_SIZE, false);
>  	if (ret)
>  		goto out;
> -- 
> 2.20.1
> 

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