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path: root/libbb/udp_io.c (plain)
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1/* vi: set sw=4 ts=4: */
2/*
3 * Utility routines.
4 *
5 * Copyright (C) 2007 Denys Vlasenko
6 *
7 * Licensed under GPLv2, see file LICENSE in this source tree.
8 */
9#include "libbb.h"
10
11#if defined(IPV6_PKTINFO) && defined(__BIONIC__) && !defined(BIONIC_ICS)
12// now included in Bionic ICS
13struct in6_pktinfo {
14 struct in6_addr ipi6_addr; // src/dst IPv6 address
15 unsigned int ipi6_ifindex; // send/recv if index
16};
17#endif
18
19/*
20 * This asks kernel to let us know dst addr/port of incoming packets
21 * We don't check for errors here. Not supported == won't be used
22 */
23void FAST_FUNC
24socket_want_pktinfo(int fd UNUSED_PARAM)
25{
26#ifdef IP_PKTINFO
27 setsockopt_1(fd, IPPROTO_IP, IP_PKTINFO);
28#endif
29#if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
30 setsockopt_1(fd, IPPROTO_IPV6, IPV6_PKTINFO);
31#endif
32}
33
34
35ssize_t FAST_FUNC
36send_to_from(int fd, void *buf, size_t len, int flags,
37 const struct sockaddr *to,
38 const struct sockaddr *from,
39 socklen_t tolen)
40{
41#ifndef IP_PKTINFO
42 (void)from; /* suppress "unused from" warning */
43 return sendto(fd, buf, len, flags, to, tolen);
44#else
45 struct iovec iov[1];
46 struct msghdr msg;
47 union {
48 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
49# if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
50 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
51# endif
52 } u;
53 struct cmsghdr* cmsgptr;
54
55 if (from->sa_family != AF_INET
56# if ENABLE_FEATURE_IPV6
57 && from->sa_family != AF_INET6
58# endif
59 ) {
60 /* ANY local address */
61 return sendto(fd, buf, len, flags, to, tolen);
62 }
63
64 /* man recvmsg and man cmsg is needed to make sense of code below */
65
66 iov[0].iov_base = buf;
67 iov[0].iov_len = len;
68
69 memset(&u, 0, sizeof(u));
70
71 memset(&msg, 0, sizeof(msg));
72 msg.msg_name = (void *)(struct sockaddr *)to; /* or compiler will annoy us */
73 msg.msg_namelen = tolen;
74 msg.msg_iov = iov;
75 msg.msg_iovlen = 1;
76 msg.msg_control = &u;
77 msg.msg_controllen = sizeof(u);
78 msg.msg_flags = flags;
79
80 cmsgptr = CMSG_FIRSTHDR(&msg);
81 /*
82 * Users report that to->sa_family can be AF_INET6 too,
83 * if "to" was acquired by recv_from_to(). IOW: recv_from_to()
84 * was seen showing IPv6 "from" even when the destination
85 * of received packet (our local address) was IPv4.
86 */
87 if (/* to->sa_family == AF_INET && */ from->sa_family == AF_INET) {
88 struct in_pktinfo *pktptr;
89 cmsgptr->cmsg_level = IPPROTO_IP;
90 cmsgptr->cmsg_type = IP_PKTINFO;
91 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
92 pktptr = (struct in_pktinfo *)(CMSG_DATA(cmsgptr));
93 /*pktptr->ipi_ifindex = 0; -- already done by memset(u...) */
94 /* In general, CMSG_DATA() can be unaligned, but in this case
95 * we know for sure it is sufficiently aligned:
96 * CMSG_FIRSTHDR simply returns &u above,
97 * and CMSG_DATA returns &u + size_t + int + int.
98 * Thus direct assignment is ok:
99 */
100 pktptr->ipi_spec_dst = ((struct sockaddr_in*)from)->sin_addr;
101 }
102# if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
103 else if (/* to->sa_family == AF_INET6 && */ from->sa_family == AF_INET6) {
104 struct in6_pktinfo *pktptr;
105 cmsgptr->cmsg_level = IPPROTO_IPV6;
106 cmsgptr->cmsg_type = IPV6_PKTINFO;
107 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
108 pktptr = (struct in6_pktinfo *)(CMSG_DATA(cmsgptr));
109 /* pktptr->ipi6_ifindex = 0; -- already done by memset(u...) */
110 pktptr->ipi6_addr = ((struct sockaddr_in6*)from)->sin6_addr;
111 }
112# endif
113 msg.msg_controllen = cmsgptr->cmsg_len;
114
115 return sendmsg(fd, &msg, flags);
116#endif
117}
118
119/* NB: this will never set port# in 'to'!
120 * _Only_ IP/IPv6 address part of 'to' is _maybe_ modified.
121 * Typical usage is to preinit 'to' with "default" value
122 * before calling recv_from_to(). */
123ssize_t FAST_FUNC
124recv_from_to(int fd, void *buf, size_t len, int flags,
125 struct sockaddr *from, struct sockaddr *to,
126 socklen_t sa_size)
127{
128#ifndef IP_PKTINFO
129 (void)to; /* suppress "unused to" warning */
130 return recvfrom(fd, buf, len, flags, from, &sa_size);
131#else
132 /* man recvmsg and man cmsg is needed to make sense of code below */
133 struct iovec iov[1];
134 union {
135 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
136# if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
137 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
138# endif
139 } u;
140 struct cmsghdr *cmsgptr;
141 struct msghdr msg;
142 ssize_t recv_length;
143
144 iov[0].iov_base = buf;
145 iov[0].iov_len = len;
146
147 memset(&msg, 0, sizeof(msg));
148 msg.msg_name = (struct sockaddr *)from;
149 msg.msg_namelen = sa_size;
150 msg.msg_iov = iov;
151 msg.msg_iovlen = 1;
152 msg.msg_control = &u;
153 msg.msg_controllen = sizeof(u);
154
155 recv_length = recvmsg(fd, &msg, flags);
156 if (recv_length < 0)
157 return recv_length;
158
159# define to4 ((struct sockaddr_in*)to)
160# define to6 ((struct sockaddr_in6*)to)
161 /* Here we try to retrieve destination IP and memorize it */
162 for (cmsgptr = CMSG_FIRSTHDR(&msg);
163 cmsgptr != NULL;
164 cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)
165 ) {
166 if (cmsgptr->cmsg_level == IPPROTO_IP
167 && cmsgptr->cmsg_type == IP_PKTINFO
168 ) {
169 const int IPI_ADDR_OFF = offsetof(struct in_pktinfo, ipi_addr);
170 to->sa_family = AF_INET;
171 /*# define pktinfo(cmsgptr) ( (struct in_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
172 /*to4->sin_addr = pktinfo(cmsgptr)->ipi_addr; - may be unaligned */
173 memcpy(&to4->sin_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI_ADDR_OFF, sizeof(to4->sin_addr));
174 /*to4->sin_port = 123; - this data is not supplied by kernel */
175 break;
176 }
177# if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
178 if (cmsgptr->cmsg_level == IPPROTO_IPV6
179 && cmsgptr->cmsg_type == IPV6_PKTINFO
180 ) {
181 const int IPI6_ADDR_OFF = offsetof(struct in6_pktinfo, ipi6_addr);
182 to->sa_family = AF_INET6;
183 /*# define pktinfo(cmsgptr) ( (struct in6_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
184 /*to6->sin6_addr = pktinfo(cmsgptr)->ipi6_addr; - may be unaligned */
185 memcpy(&to6->sin6_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI6_ADDR_OFF, sizeof(to6->sin6_addr));
186 /*to6->sin6_port = 123; */
187 break;
188 }
189# endif
190 }
191 return recv_length;
192#endif
193}
194
generated by cgit at 2024-05-15 11:23:20 (GMT)