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Re: [Patch 1/1] CLD: Introduce the "New CLD" API



On 02/09/2010 12:35 AM, Pete Zaitcev wrote:
On Mon, 08 Feb 2010 23:55:03 -0500
Jeff Garzik<jeff@xxxxxxxxxx>  wrote:

-	if (cldc_getaddr(&host_list, hostb, NULL))
+	if (cldc_getaddr(&host_list, hostb,&ncld_log))
    		return 1001;

Logging pointer should be supplied by the caller...  that is the larger
bug.  Needing a no-op log function is just an indication of that.

I did it before, but then every client, without exception, needed
to include<stdarg.h>   and provide the log. And what for? This is
STUPID and proof is in the pudding: your getsrvinfo does not do
anything of the sort.

Possibly true -- but it is worse to introduce internal inconsistencies.
   It is far better to remove debugging statements completely than to
create inconsistent usage.

Hmm, you may be right about that.

Might as well replace cldc_getadd with getsrvinfo
and then everyone becomes happy.

Seems a good fit :)

How far along were you with getsrvinfo? I only have the header
that you sent to the list just before Christmas.

Coding complete, but needed testing. Probably works, since it came from working code. See attached.

	Jeff


#ifndef __GETSRVINFO_H__
#define __GETSRVINFO_H__

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>

struct srvinfo;

enum srvinfo_error_codes {
	ESI_NONE		= 0,	/* no error */
	ESI_CORRUPT		= 1,	/* server returned bad data */
	ESI_FAIL		= 2,	/* server returned permanent failure */
	ESI_AGAIN		= 3,	/* server returned temporary failure;
					 * try again later.*/
	ESI_OOM			= 4,	/* internal memory alloc failed */
	ESI_INVAL		= 5,	/* invalid argument(s) */
};

enum srvinfo_flags {
	FSI_NO_ADDR		= (1U << 0),  /* skip host->addrs lookup */
};

struct srvinfo {
	unsigned int		si_prio;    /* SRV priority */
	unsigned int		si_weight;  /* SRV weight */
	char			*si_target; /* SRV target domainname */
	unsigned short		si_port;    /* SRV port */

	struct addrinfo		*si_addr;   /* addresses returned
					     * from getaddrinfo(3) lookup
					     * on si_target */
	struct srvinfo		*si_next;   /* next srvinfo in result list */
};

extern int getsrvinfo(const char *service_name, const char *domain_name,
		      const struct addrinfo *hints,
		      unsigned int flags, struct srvinfo **res);
extern void freesrvinfo(struct srvinfo *res);
extern const char *gsi_strerror(int errcode);

#endif /* __GETSRVINFO_H__ */
/*
 * Copyright 2009 Red Hat, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <netdb.h>
#include <resolv.h>
#include "getsrvinfo.h"

#define __must_be_array(a) \
	(__builtin_types_compatible_p(typeof(a), typeof(&a[0])))
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))

enum {
	gsi_max_dom_name_sz		= 64,
	gsi_dns_buf_sz			= 1024,
};

static int fill_srvinfo(struct srvinfo *si,
			const struct addrinfo *hints,
			unsigned int gsi_flags,
			unsigned int priority,
			unsigned int weight, unsigned int port,
			unsigned int nlen, const char *name)
{
	char portstr[11];
	char *hostname;
	struct addrinfo *res0 = NULL;
	int rc = 0;

	sprintf(portstr, "%u", port);

	hostname = malloc(nlen + 1);
	if (!hostname)
		return -ENOMEM;

	memcpy(hostname, name, nlen);
	hostname[nlen] = 0;

	if (!(gsi_flags & FSI_NO_ADDR)) {
		rc = getaddrinfo(hostname, portstr, hints, &res0);

		/* because we do not wish failure of one lookup
		 * to cause failure of the entire operation,
		 * we simply record the lack of an address (NULL)
		 * and move on.
		 */
		if (rc)
			res0 = NULL;
	}

	si->si_prio = priority;
	si->si_weight = weight;
	si->si_target = hostname;
	si->si_port = port;

	si->si_addr = res0;
	si->si_next = NULL;

	return 0;
}

void freesrvinfo(struct srvinfo *res)
{
	while (res) {
		struct srvinfo *tmp;
		
		tmp = res;
		res = res->si_next;

		if (tmp->si_addr)
			freeaddrinfo(tmp->si_addr);
		free(tmp->si_target);
		free(tmp);
	}
}

int getsrvinfo(const char *service_name, const char *domain_name,
	       const struct addrinfo *hints, unsigned int gsi_flags,
	       struct srvinfo **res_out)
{
	unsigned char resp[gsi_dns_buf_sz];
	int rlen;
	ns_msg nsb;
	ns_rr rrb;
	int rrlen;
	char hostb[gsi_max_dom_name_sz];
	struct srvinfo *si, *res = NULL, *res_last = NULL;
	const unsigned char *p;
	int rc, gsi_rc, i;

	if (!domain_name || !res_out)
		return ESI_INVAL;

	*res_out = NULL;

	/* we concatencate service_name and domain_name as a helpful
	 * service for the caller, because it is very common
	 * that service_name is either completely static, or at least
	 * stored in a separate variable from domain_name.
	 */
	if (service_name) {
		char *name;
		size_t name_len;
		int has_dot;

		has_dot = (service_name[strlen(service_name) - 1] == '.');
		name_len = strlen(service_name) + strlen(domain_name) +
			   (has_dot ? 0 : 1) + 1;

		name = malloc(name_len);
		if (!name)
			return ESI_OOM;

		snprintf(name, name_len, "%s%s%s", service_name,
			     has_dot ? "" : ".",
			     domain_name);
			
		rc = res_search(name, ns_c_in, ns_t_srv, resp, sizeof(resp));

		free(name);
	} else {
		rc = res_search(domain_name, ns_c_in, ns_t_srv,
				resp, sizeof(resp));
	}

	/* parse resolver return value */
	if (rc < 0) {
		switch (h_errno) {
		case TRY_AGAIN:
			return ESI_AGAIN;
		case HOST_NOT_FOUND:
		case NO_DATA:
		case NO_RECOVERY:
		default:
			return ESI_FAIL;
		}
	}
	rlen = rc;

	if (rlen == 0)
		return ESI_FAIL;

	/* set up DNS result parse */
	if (ns_initparse(resp, rlen, &nsb) < 0)
		return ESI_CORRUPT;

	/* iterate through each answer.  Because DNS packets may
	 * be truncated, we do not signal an error on
	 * short-length faults found during packet parsing
	 */
	for (i = 0; i < ns_msg_count(nsb, ns_s_an); i++) {
		rc = ns_parserr(&nsb, ns_s_an, i, &rrb);
		if (rc < 0)
			continue;

		if (ns_rr_class(rrb) != ns_c_in)
			continue;

		switch (ns_rr_type(rrb)) {
		case ns_t_srv:
			rrlen = ns_rr_rdlen(rrb);
			if (rrlen < 8) {	/* 2+2+2 and 2 for host */
				break;
			}
			p = ns_rr_rdata(rrb);
			rc = dn_expand(resp, resp+rlen, p+6,
				       hostb, gsi_max_dom_name_sz);
			if (rc < 0) {
				break;
			}
			if (rc < 2) {
				break;
			}

			si = malloc(sizeof(*si));
			if (!si) {
				gsi_rc = ESI_OOM;
				goto err_out;
			}

			if (fill_srvinfo(si, hints, gsi_flags,
					 ns_get16(p+0),
					 ns_get16(p+2),
					 ns_get16(p+4),
					 rc, hostb)) {
				free(si);
				gsi_rc = ESI_OOM;
				goto err_out;
			}

			/* if first item, set BOL-ptr */
			if (!res)
				res = si;

			/* append to EOL */
			if (res_last)
				res_last->si_next = si;
			res_last = si;

			break;

		case ns_t_cname:	/* impossible, but ... ? */
		default:
			break;
		}
	}

	*res_out = res;
	return ESI_NONE;

err_out:
	freesrvinfo(res);
	return gsi_rc;
}

static const char *gsi_error_str[] = {
	[ESI_NONE]		= "no error",
	[ESI_CORRUPT]		= "server returned bad data",
	[ESI_FAIL]		= "server returned permanent failure",
	[ESI_AGAIN]		= "server returned temporary failure",
	[ESI_OOM]		= "internal memory alloc failed",
	[ESI_INVAL]		= "invalid argument(s)",
};

const char *gsi_strerror(int errcode)
{
	if (errcode < 0 || errcode >= ARRAY_SIZE(gsi_error_str))
		return NULL;
	
	return gsi_error_str[errcode];
}


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