socktohost.c revision 290001 
1/*
2 * socktoa - return a numeric host name from a sockaddr_storage structure
3 */
4#include <config.h>
5#include <sys/types.h>
6#ifdef HAVE_SYS_SOCKET_H
7#include <sys/socket.h>
8#endif
9#ifdef HAVE_NETINET_IN_H
10#include <netinet/in.h>
11#endif
12
13#include <arpa/inet.h>
14
15#include <stdio.h>
16
17#include "ntp_fp.h"
18#include "lib_strbuf.h"
19#include "ntp_stdlib.h"
20#include "ntp.h"
21#include "ntp_debug.h"
22
23
24const char *
25socktohost(
26	const sockaddr_u *sock
27	)
28{
29	const char		svc[] = "ntp";
30	char *			pbuf;
31	char *			pliar;
32	int			gni_flags;
33	struct addrinfo		hints;
34	struct addrinfo *	alist;
35	struct addrinfo *	ai;
36	sockaddr_u		addr;
37	size_t			octets;
38	int			a_info;
39
40	/* reverse the address to purported DNS name */
41	LIB_GETBUF(pbuf);
42	gni_flags = NI_DGRAM | NI_NAMEREQD;
43	if (getnameinfo(&sock->sa, SOCKLEN(sock), pbuf, LIB_BUFLENGTH,
44			NULL, 0, gni_flags))
45		return stoa(sock);	/* use address */
46
47	TRACE(1, ("%s reversed to %s\n", stoa(sock), pbuf));
48
49	/*
50	 * Resolve the reversed name and make sure the reversed address
51	 * is among the results.
52	 */
53	ZERO(hints);
54	hints.ai_family = AF(sock);
55	hints.ai_protocol = IPPROTO_UDP;
56	hints.ai_socktype = SOCK_DGRAM;
57	hints.ai_flags = 0;
58	alist = NULL;
59
60	a_info = getaddrinfo(pbuf, svc, &hints, &alist);
61	if (a_info == EAI_NONAME
62#ifdef EAI_NODATA
63	    || a_info == EAI_NODATA
64#endif
65	   ) {
66		hints.ai_flags = AI_CANONNAME;
67#ifdef AI_ADDRCONFIG
68		hints.ai_flags |= AI_ADDRCONFIG;
69#endif
70		a_info = getaddrinfo(pbuf, svc, &hints, &alist);
71	}
72#ifdef AI_ADDRCONFIG
73	/* Some older implementations don't like AI_ADDRCONFIG. */
74	if (a_info == EAI_BADFLAGS) {
75		hints.ai_flags &= ~AI_ADDRCONFIG;
76		a_info = getaddrinfo(pbuf, svc, &hints, &alist);
77	}
78#endif
79	if (a_info)
80		goto forward_fail;
81
82	INSIST(alist != NULL);
83
84	for (ai = alist; ai != NULL; ai = ai->ai_next) {
85		/*
86		 * Make a convenience sockaddr_u copy from ai->ai_addr
87		 * because casting from sockaddr * to sockaddr_u * is
88		 * risking alignment problems on platforms where
89		 * sockaddr_u has stricter alignment than sockaddr,
90		 * such as sparc.
91		 */
92		ZERO_SOCK(&addr);
93		octets = min(sizeof(addr), ai->ai_addrlen);
94		memcpy(&addr, ai->ai_addr, octets);
95		if (SOCK_EQ(sock, &addr))
96			break;
97	}
98	freeaddrinfo(alist);
99
100	if (ai != NULL)
101		return pbuf;	/* forward check passed */
102
103    forward_fail:
104	TRACE(1, ("%s forward check lookup fail: %s\n", pbuf,
105		  gai_strerror(a_info)));
106	LIB_GETBUF(pliar);
107	snprintf(pliar, LIB_BUFLENGTH, "%s (%s)", stoa(sock), pbuf);
108
109	return pliar;
110}
111