1 /* vi: set sw=4 ts=4: */
5 * Copyright (C) 2007 Denys Vlasenko
7 * Licensed under GPLv2, see file LICENSE in this source tree.
12 * This asks kernel to let us know dst addr/port of incoming packets
13 * We don't check for errors here. Not supported == won't be used
16 socket_want_pktinfo(int fd UNUSED_PARAM)
19 setsockopt_1(fd, IPPROTO_IP, IP_PKTINFO);
21 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
22 setsockopt_1(fd, IPPROTO_IPV6, IPV6_PKTINFO);
28 send_to_from(int fd, void *buf, size_t len, int flags,
29 const struct sockaddr *to,
30 const struct sockaddr *from,
34 (void)from; /* suppress "unused from" warning */
35 return sendto(fd, buf, len, flags, to, tolen);
40 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
41 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
42 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
45 struct cmsghdr* cmsgptr;
47 if (from->sa_family != AF_INET
48 # if ENABLE_FEATURE_IPV6
49 && from->sa_family != AF_INET6
52 /* ANY local address */
53 return sendto(fd, buf, len, flags, to, tolen);
56 /* man recvmsg and man cmsg is needed to make sense of code below */
58 iov[0].iov_base = buf;
61 memset(&u, 0, sizeof(u));
63 memset(&msg, 0, sizeof(msg));
64 msg.msg_name = (void *)(struct sockaddr *)to; /* or compiler will annoy us */
65 msg.msg_namelen = tolen;
69 msg.msg_controllen = sizeof(u);
70 msg.msg_flags = flags;
72 cmsgptr = CMSG_FIRSTHDR(&msg);
74 * Users report that to->sa_family can be AF_INET6 too,
75 * if "to" was acquired by recv_from_to(). IOW: recv_from_to()
76 * was seen showing IPv6 "from" even when the destination
77 * of received packet (our local address) was IPv4.
79 if (/* to->sa_family == AF_INET && */ from->sa_family == AF_INET) {
80 struct in_pktinfo *pktptr;
81 cmsgptr->cmsg_level = IPPROTO_IP;
82 cmsgptr->cmsg_type = IP_PKTINFO;
83 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
84 pktptr = (struct in_pktinfo *)(CMSG_DATA(cmsgptr));
85 /*pktptr->ipi_ifindex = 0; -- already done by memset(u...) */
86 /* In general, CMSG_DATA() can be unaligned, but in this case
87 * we know for sure it is sufficiently aligned:
88 * CMSG_FIRSTHDR simply returns &u above,
89 * and CMSG_DATA returns &u + size_t + int + int.
90 * Thus direct assignment is ok:
92 pktptr->ipi_spec_dst = ((struct sockaddr_in*)from)->sin_addr;
94 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
95 else if (/* to->sa_family == AF_INET6 && */ from->sa_family == AF_INET6) {
96 struct in6_pktinfo *pktptr;
97 cmsgptr->cmsg_level = IPPROTO_IPV6;
98 cmsgptr->cmsg_type = IPV6_PKTINFO;
99 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
100 pktptr = (struct in6_pktinfo *)(CMSG_DATA(cmsgptr));
101 /* pktptr->ipi6_ifindex = 0; -- already done by memset(u...) */
102 pktptr->ipi6_addr = ((struct sockaddr_in6*)from)->sin6_addr;
105 msg.msg_controllen = cmsgptr->cmsg_len;
107 return sendmsg(fd, &msg, flags);
111 /* NB: this will never set port# in 'to'!
112 * _Only_ IP/IPv6 address part of 'to' is _maybe_ modified.
113 * Typical usage is to preinit 'to' with "default" value
114 * before calling recv_from_to(). */
116 recv_from_to(int fd, void *buf, size_t len, int flags,
117 struct sockaddr *from, struct sockaddr *to,
121 (void)to; /* suppress "unused to" warning */
122 return recvfrom(fd, buf, len, flags, from, &sa_size);
124 /* man recvmsg and man cmsg is needed to make sense of code below */
127 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
128 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
129 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
132 struct cmsghdr *cmsgptr;
136 iov[0].iov_base = buf;
137 iov[0].iov_len = len;
139 memset(&msg, 0, sizeof(msg));
140 msg.msg_name = (struct sockaddr *)from;
141 msg.msg_namelen = sa_size;
144 msg.msg_control = &u;
145 msg.msg_controllen = sizeof(u);
147 recv_length = recvmsg(fd, &msg, flags);
151 # define to4 ((struct sockaddr_in*)to)
152 # define to6 ((struct sockaddr_in6*)to)
153 /* Here we try to retrieve destination IP and memorize it */
154 for (cmsgptr = CMSG_FIRSTHDR(&msg);
156 cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)
158 if (cmsgptr->cmsg_level == IPPROTO_IP
159 && cmsgptr->cmsg_type == IP_PKTINFO
161 const int IPI_ADDR_OFF = offsetof(struct in_pktinfo, ipi_addr);
162 to->sa_family = AF_INET;
163 /*# define pktinfo(cmsgptr) ( (struct in_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
164 /*to4->sin_addr = pktinfo(cmsgptr)->ipi_addr; - may be unaligned */
165 memcpy(&to4->sin_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI_ADDR_OFF, sizeof(to4->sin_addr));
166 /*to4->sin_port = 123; - this data is not supplied by kernel */
169 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
170 if (cmsgptr->cmsg_level == IPPROTO_IPV6
171 && cmsgptr->cmsg_type == IPV6_PKTINFO
173 const int IPI6_ADDR_OFF = offsetof(struct in6_pktinfo, ipi6_addr);
174 to->sa_family = AF_INET6;
175 /*# define pktinfo(cmsgptr) ( (struct in6_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
176 /*to6->sin6_addr = pktinfo(cmsgptr)->ipi6_addr; - may be unaligned */
177 memcpy(&to6->sin6_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI6_ADDR_OFF, sizeof(to6->sin6_addr));
178 /*to6->sin6_port = 123; */