1/* vi: set sw=4 ts=4: */
2/*
3 * Utility routines.
4 *
5 * Copyright (C) 2007 Denis Vlasenko
6 *
7 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
8 */
9
10#include "libbb.h"
11
12/*
13 * This asks kernel to let us know dst addr/port of incoming packets
14 * We don't check for errors here. Not supported == won't be used
15 */
16void
17socket_want_pktinfo(int fd)
18{
19#ifdef IP_PKTINFO
20	setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &const_int_1, sizeof(int));
21#endif
22#if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
23	setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &const_int_1, sizeof(int));
24#endif
25}
26
27
28#ifdef UNUSED
29ssize_t
30send_to_from(int fd, void *buf, size_t len, int flags,
31		const struct sockaddr *from, const struct sockaddr *to,
32		socklen_t tolen)
33{
34#ifndef IP_PKTINFO
35	return sendto(fd, buf, len, flags, to, tolen);
36#else
37	struct iovec iov[1];
38	struct msghdr msg;
39	char cbuf[sizeof(struct in_pktinfo)
40#if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
41		| sizeof(struct in6_pktinfo) /* (a|b) is poor man's max(a,b) */
42#endif
43	];
44	struct cmsghdr* cmsgptr;
45
46	if (from->sa_family != AF_INET
47#if ENABLE_FEATURE_IPV6
48	 && from->sa_family != AF_INET6
49#endif
50	) {
51		/* ANY local address */
52		return sendto(fd, buf, len, flags, to, tolen);
53	}
54
55	/* man recvmsg and man cmsg is needed to make sense of code below */
56
57	iov[0].iov_base = buf;
58	iov[0].iov_len = len;
59
60	memset(cbuf, 0, sizeof(cbuf));
61
62	memset(&msg, 0, sizeof(msg));
63	msg.msg_name = (void *)(struct sockaddr *)to; /* or compiler will annoy us */
64	msg.msg_namelen = tolen;
65	msg.msg_iov = iov;
66	msg.msg_iovlen = 1;
67	msg.msg_control = cbuf;
68	msg.msg_controllen = sizeof(cbuf);
69	msg.msg_flags = flags;
70
71	cmsgptr = CMSG_FIRSTHDR(&msg);
72	if (to->sa_family == AF_INET && from->sa_family == AF_INET) {
73		struct in_pktinfo *pktptr;
74		cmsgptr->cmsg_level = IPPROTO_IP;
75		cmsgptr->cmsg_type = IP_PKTINFO;
76		cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
77		pktptr = (struct in_pktinfo *)(CMSG_DATA(cmsgptr));
78		/* pktptr->ipi_ifindex = 0; -- already done by memset(cbuf...) */
79		pktptr->ipi_spec_dst = ((struct sockaddr_in*)from)->sin_addr;
80	}
81#if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
82	else if (to->sa_family == AF_INET6 && from->sa_family == AF_INET6) {
83		struct in6_pktinfo *pktptr;
84		cmsgptr->cmsg_level = IPPROTO_IPV6;
85		cmsgptr->cmsg_type = IPV6_PKTINFO;
86		cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
87		pktptr = (struct in6_pktinfo *)(CMSG_DATA(cmsgptr));
88		/* pktptr->ipi6_ifindex = 0; -- already done by memset(cbuf...) */
89		pktptr->ipi6_addr = ((struct sockaddr_in6*)from)->sin6_addr;
90	}
91#endif
92	return sendmsg(fd, &msg, flags);
93#endif
94}
95#endif /* UNUSED */
96
97/* NB: this will never set port# in 'to'!
98 * _Only_ IP/IPv6 address part of 'to' is _maybe_ modified.
99 * Typical usage is to preinit 'to' with "default" value
100 * before calling recv_from_to(). */
101ssize_t
102recv_from_to(int fd, void *buf, size_t len, int flags,
103		struct sockaddr *from, struct sockaddr *to,
104		socklen_t sa_size)
105{
106#ifndef IP_PKTINFO
107	return recvfrom(fd, buf, len, flags, from, &sa_size);
108#else
109	/* man recvmsg and man cmsg is needed to make sense of code below */
110	struct iovec iov[1];
111	union {
112		char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
113		char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
114	} u;
115	struct cmsghdr *cmsgptr;
116	struct msghdr msg;
117	socklen_t recv_length;
118
119	iov[0].iov_base = buf;
120	iov[0].iov_len = len;
121
122	memset(&msg, 0, sizeof(msg));
123	msg.msg_name = (struct sockaddr *)from;
124	msg.msg_namelen = sa_size;
125	msg.msg_iov = iov;
126	msg.msg_iovlen = 1;
127	msg.msg_control = &u;
128	msg.msg_controllen = sizeof(u);
129
130	recv_length = recvmsg(fd, &msg, flags);
131	if (recv_length < 0)
132		return recv_length;
133
134	/* Here we try to retrieve destination IP and memorize it */
135	for (cmsgptr = CMSG_FIRSTHDR(&msg);
136			cmsgptr != NULL;
137			cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)
138	) {
139		if (cmsgptr->cmsg_level == IPPROTO_IP
140		 && cmsgptr->cmsg_type == IP_PKTINFO
141		) {
142#define pktinfo(cmsgptr) ( (struct in_pktinfo*)(CMSG_DATA(cmsgptr)) )
143			to->sa_family = AF_INET;
144			((struct sockaddr_in*)to)->sin_addr = pktinfo(cmsgptr)->ipi_addr;
145			/* ((struct sockaddr_in*)to)->sin_port = 123; */
146#undef pktinfo
147			break;
148		}
149#if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
150		if (cmsgptr->cmsg_level == IPPROTO_IPV6
151		 && cmsgptr->cmsg_type == IPV6_PKTINFO
152		) {
153#define pktinfo(cmsgptr) ( (struct in6_pktinfo*)(CMSG_DATA(cmsgptr)) )
154			to->sa_family = AF_INET6;
155			((struct sockaddr_in6*)to)->sin6_addr = pktinfo(cmsgptr)->ipi6_addr;
156			/* ((struct sockaddr_in6*)to)->sin6_port = 123; */
157#undef pktinfo
158			break;
159		}
160#endif
161	}
162	return recv_length;
163#endif
164}
165