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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(fd, IPPROTO_IP, IP_PKTINFO, &const_int_1, sizeof(int));
28#endif
29#if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
30 setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &const_int_1, sizeof(int));
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 if (to->sa_family == AF_INET && from->sa_family == AF_INET) {
82 struct in_pktinfo *pktptr;
83 cmsgptr->cmsg_level = IPPROTO_IP;
84 cmsgptr->cmsg_type = IP_PKTINFO;
85 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
86 pktptr = (struct in_pktinfo *)(CMSG_DATA(cmsgptr));
87 /*pktptr->ipi_ifindex = 0; -- already done by memset(u...) */
88 /* In general, CMSG_DATA() can be unaligned, but in this case
89 * we know for sure it is sufficiently aligned:
90 * CMSG_FIRSTHDR simply returns &u above,
91 * and CMSG_DATA returns &u + size_t + int + int.
92 * Thus direct assignment is ok:
93 */
94 pktptr->ipi_spec_dst = ((struct sockaddr_in*)from)->sin_addr;
95 }
96# if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
97 else if (to->sa_family == AF_INET6 && from->sa_family == AF_INET6) {
98 struct in6_pktinfo *pktptr;
99 cmsgptr->cmsg_level = IPPROTO_IPV6;
100 cmsgptr->cmsg_type = IPV6_PKTINFO;
101 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
102 pktptr = (struct in6_pktinfo *)(CMSG_DATA(cmsgptr));
103 /* pktptr->ipi6_ifindex = 0; -- already done by memset(u...) */
104 pktptr->ipi6_addr = ((struct sockaddr_in6*)from)->sin6_addr;
105 }
106# endif
107 msg.msg_controllen = cmsgptr->cmsg_len;
108
109 return sendmsg(fd, &msg, flags);
110#endif
111}
112
113/* NB: this will never set port# in 'to'!
114 * _Only_ IP/IPv6 address part of 'to' is _maybe_ modified.
115 * Typical usage is to preinit 'to' with "default" value
116 * before calling recv_from_to(). */
117ssize_t FAST_FUNC
118recv_from_to(int fd, void *buf, size_t len, int flags,
119 struct sockaddr *from, struct sockaddr *to,
120 socklen_t sa_size)
121{
122#ifndef IP_PKTINFO
123 (void)to; /* suppress "unused to" warning */
124 return recvfrom(fd, buf, len, flags, from, &sa_size);
125#else
126 /* man recvmsg and man cmsg is needed to make sense of code below */
127 struct iovec iov[1];
128 union {
129 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
130# if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
131 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
132# endif
133 } u;
134 struct cmsghdr *cmsgptr;
135 struct msghdr msg;
136 ssize_t recv_length;
137
138 iov[0].iov_base = buf;
139 iov[0].iov_len = len;
140
141 memset(&msg, 0, sizeof(msg));
142 msg.msg_name = (struct sockaddr *)from;
143 msg.msg_namelen = sa_size;
144 msg.msg_iov = iov;
145 msg.msg_iovlen = 1;
146 msg.msg_control = &u;
147 msg.msg_controllen = sizeof(u);
148
149 recv_length = recvmsg(fd, &msg, flags);
150 if (recv_length < 0)
151 return recv_length;
152
153# define to4 ((struct sockaddr_in*)to)
154# define to6 ((struct sockaddr_in6*)to)
155 /* Here we try to retrieve destination IP and memorize it */
156 for (cmsgptr = CMSG_FIRSTHDR(&msg);
157 cmsgptr != NULL;
158 cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)
159 ) {
160 if (cmsgptr->cmsg_level == IPPROTO_IP
161 && cmsgptr->cmsg_type == IP_PKTINFO
162 ) {
163 const int IPI_ADDR_OFF = offsetof(struct in_pktinfo, ipi_addr);
164 to->sa_family = AF_INET;
165 /*# define pktinfo(cmsgptr) ( (struct in_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
166 /*to4->sin_addr = pktinfo(cmsgptr)->ipi_addr; - may be unaligned */
167 memcpy(&to4->sin_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI_ADDR_OFF, sizeof(to4->sin_addr));
168 /*to4->sin_port = 123; - this data is not supplied by kernel */
169 break;
170 }
171# if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
172 if (cmsgptr->cmsg_level == IPPROTO_IPV6
173 && cmsgptr->cmsg_type == IPV6_PKTINFO
174 ) {
175 const int IPI6_ADDR_OFF = offsetof(struct in6_pktinfo, ipi6_addr);
176 to->sa_family = AF_INET6;
177 /*# define pktinfo(cmsgptr) ( (struct in6_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
178 /*to6->sin6_addr = pktinfo(cmsgptr)->ipi6_addr; - may be unaligned */
179 memcpy(&to6->sin6_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI6_ADDR_OFF, sizeof(to6->sin6_addr));
180 /*to6->sin6_port = 123; */
181 break;
182 }
183# endif
184 }
185 return recv_length;
186#endif
187}
188
generated by cgit at 2024-05-15 23:21:58 (GMT)