Attachment 311401 Details for Bug 453325 – Example code used in server to look up DNS SRV records

Example code used in server to look up DNS SRV records

server.c (text/plain), 4.87 KB, created by Jeff Garzik on 2008-07-09 18:36:28 UTC

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Creator: Jeff Garzik

Created: 2008-07-09 18:36:28 UTC

Size: 4.87 KB

patch

obsolete

>#define _GNU_SOURCE
>#include <sys/types.h>
>#include <sys/stat.h>
>#include <sys/socket.h>
>#include <sys/epoll.h>
>#include <fcntl.h>
>#include <stdlib.h>
>#include <unistd.h>
>#include <string.h>
>#include <netdb.h>
>#include <stdio.h>
>#include <signal.h>
>#include <locale.h>
>#include <netinet/in.h>
>#include <stdbool.h>
>#include <arpa/nameser.h>
>#include <resolv.h>
>#include <syslog.h>
>#include <argp.h>
>
>enum {
>	CLD_EPOLL_INIT_SIZE	= 200,		/* passed to epoll_create(2) */
>	CLD_EPOLL_MAX_EVT	= 100,		/* max events per poll */
>	CLD_DEF_PORT		= 8080,		/* default bind(2) port */
>
>	SFL_FOREGROUND		= (1 << 0),	/* run in foreground */
>};
>
>enum server_poll_type {
>	spt_udp_srv,				/* UDP server */
>};
>
>enum {
>	UDP_MAX_SZ		= 1280,
>};
>
>struct server_poll {
>	enum server_poll_type	poll_type;	/* spt_xxx above */
>	void			*ptr;
>};
>
>struct server_stats {
>	unsigned long		poll;		/* number polls */
>	unsigned long		event;		/* events dispatched */
>	unsigned long		udp_rx;		/* UDP RX'd msgs */
>	unsigned long		udp_rx_bytes;	/* UDP RX'd bytes */
>	unsigned long		udp_bad;	/* Invalid UDP pkts */
>	unsigned long		udp_content;	/* UDP decrypt/check failed */
>	unsigned long		max_evt;	/* epoll events max'd out */
>	unsigned long		cli_rx;		/* client messages RX'd */
>	unsigned long		peer_rx;	/* peer messages RX'd */
>};
>
>struct list_head {
>        struct list_head *next, *prev;
>};
>
>struct peer {
>	struct list_head	node;
>
>	int			prio;
>	int			weight;
>	int			port;
>
>	char			name[64];
>	char			addrname[64];
>
>	struct sockaddr		addr;
>	size_t			addrlen;
>};
>
>struct server {
>	unsigned long		flags;		/* SFL_xxx above */
>
>	char			*data_dir;	/* database/log dir */
>	char			*pid_file;	/* PID file */
>
>	int			port;		/* bind port */
>
>	int			epoll_fd;	/* epoll fd */
>
>	int			udp_fd;		/* UDP server desc */
>	struct server_poll	udp_poll;	/* poll info */
>	struct epoll_event	udp_evt;	/* epoll info */
>
>	struct server_stats	stats;		/* global statistics */
>
>	char			*peer_srv;	/* DNS SRV name */
>	struct list_head	peers;
>};
>
>
>static struct server cld_srv = {
>	.peer_srv		= "yyz.home.",
>};
>
>static void die(const char *msg)
>{
>	syslog(LOG_ERR, "%s", msg);
>	exit(1);
>}
>
>static int peer_push_one(uint16_t prio, uint16_t weight, uint16_t port,
>			 const char *target, struct sockaddr *addr,
>			 size_t addrlen)
>{
>	struct peer *peer;
>
>	peer = calloc(1, sizeof(*peer));
>	if (!peer) {
>		syslog(LOG_ERR, "OOM in peer_push_one");
>		return 0;
>	}
>
>#if 0
>	INIT_LIST_HEAD(&peer->node);
>#endif
>
>	peer->prio = prio;
>	peer->weight = weight;
>	peer->port = port;
>	strcpy(peer->name, target);
>	memcpy(&peer->addr, addr, addrlen);
>	peer->addrlen = addrlen;
>
>	if (getnameinfo(addr, addrlen, peer->addrname, sizeof(peer->addrname),
>			NULL, 0, NI_NUMERICHOST | NI_NUMERICSERV)) {
>		syslog(LOG_ERR, "getnameinfo failed");
>		goto err_out;
>	}
>
>#if 0
>	list_add_tail(&peer->node, &cld_srv.peers);
>#endif
>
>	syslog(LOG_INFO, "peer %s:%d added",
>	       peer->addrname,
>	       peer->port);
>
>	return 1;
>
>err_out:
>	free(peer);
>	return 0;
>}
>
>static void peer_push(uint16_t prio, uint16_t weight, uint16_t port,
>		      const char *target)
>{
>	struct addrinfo hints;
>	struct addrinfo *result, *ai;
>	int rc, res = 0;
>	char port_s[8];
>
>	memset(&hints, 0, sizeof(hints));
>	hints.ai_family = AF_UNSPEC;
>	hints.ai_socktype = SOCK_DGRAM;
>	hints.ai_flags = AI_PASSIVE;
>
>	sprintf(port_s, "%u", port);
>
>	rc = getaddrinfo(target, port_s, &hints, &result);
>	if (rc) {
>		syslog(LOG_WARNING, "getaddrinfo: %s", gai_strerror(rc));
>		return;
>	}
>
>	ai = result;
>	while (ai) {
>		res += peer_push_one(prio, weight, port, target,
>				     ai->ai_addr, ai->ai_addrlen);
>		ai = ai->ai_next;
>	}
>
>	freeaddrinfo(result);
>
>	if (!res)
>		syslog(LOG_WARNING, "SRV record '%s' yielded no peers", target);
>}
>
>static int dns_srv_lookups(void)
>{
>	unsigned char buf[4096];
>	int len, rrnum;
>	ns_msg hand;
>	ns_rr rr;
>	char peer_srv_full[64];
>
>	snprintf(peer_srv_full, sizeof(peer_srv_full),
>		 "_cld._tcp.%s", cld_srv.peer_srv);
>
>	len = res_query(peer_srv_full, ns_c_in, ns_t_srv,
>			buf, sizeof(buf));
>	if (len < 0) {
>		syslog(LOG_ERR, "DNS SRV query for %s failed", peer_srv_full);
>		return 1;
>	}
>
>	if (ns_initparse(buf, len, &hand) < 0)
>		die("ns_initparse failed");
>
>	if (ns_msg_getflag(hand, ns_f_rcode) != ns_r_noerror)
>		die("SRV lookup failed to return NOERROR (success)");
>
>	for (rrnum = 0; rrnum < ns_msg_count(hand, ns_s_an); rrnum++) {
>		const unsigned char *p;
>		uint16_t prio, weight, port;
>		char targ[65];
>
>		if (ns_parserr(&hand, ns_s_an, rrnum, &rr) < 0)
>			die("ns_parserr failed");
>
>		if (ns_rr_type(rr) != ns_t_srv)
>			die("ns_rr_type != ns_t_srv");
>		if (ns_rr_class(rr) != ns_c_in)
>			die("ns_rr_class != ns_c_in");
>
>		p = ns_rr_rdata(rr);
>
>		if (ns_rr_rdlen(rr) < (2 + 2 + 2 + 1))
>			die("rr parse: packet RDATA truncated");
>		NS_GET16(prio, p);
>		NS_GET16(weight, p);
>		NS_GET16(port, p);
>
>		if (ns_name_uncompress(ns_msg_base(hand),
>				ns_msg_end(hand), p, targ, sizeof(targ)) < 0)
>			die("ns_name_uncompress failed");
>
>		peer_push(prio, weight, port, targ);
>	}
>
>	return 0;
>}
>

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Attachments on bug 453325: 311401 | 311402