1 /* vi: set sw=4 ts=4: */
5 * Copyright (C) 2007 Denys Vlasenko
7 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
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
17 socket_want_pktinfo(int fd)
20 setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &const_int_1, sizeof(int));
22 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
23 setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &const_int_1, sizeof(int));
30 send_to_from(int fd, void *buf, size_t len, int flags,
31 const struct sockaddr *from, const struct sockaddr *to,
35 return sendto(fd, buf, len, flags, to, tolen);
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) */
44 struct cmsghdr* cmsgptr;
46 if (from->sa_family != AF_INET
47 #if ENABLE_FEATURE_IPV6
48 && from->sa_family != AF_INET6
51 /* ANY local address */
52 return sendto(fd, buf, len, flags, to, tolen);
55 /* man recvmsg and man cmsg is needed to make sense of code below */
57 iov[0].iov_base = buf;
60 memset(cbuf, 0, sizeof(cbuf));
62 memset(&msg, 0, sizeof(msg));
63 msg.msg_name = (void *)(struct sockaddr *)to; /* or compiler will annoy us */
64 msg.msg_namelen = tolen;
67 msg.msg_control = cbuf;
68 msg.msg_controllen = sizeof(cbuf);
69 msg.msg_flags = flags;
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;
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;
92 return sendmsg(fd, &msg, flags);
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(). */
102 recv_from_to(int fd, void *buf, size_t len, int flags,
103 struct sockaddr *from, struct sockaddr *to,
107 return recvfrom(fd, buf, len, flags, from, &sa_size);
109 /* man recvmsg and man cmsg is needed to make sense of code below */
112 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
113 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
115 struct cmsghdr *cmsgptr;
117 socklen_t recv_length;
119 iov[0].iov_base = buf;
120 iov[0].iov_len = len;
122 memset(&msg, 0, sizeof(msg));
123 msg.msg_name = (struct sockaddr *)from;
124 msg.msg_namelen = sa_size;
127 msg.msg_control = &u;
128 msg.msg_controllen = sizeof(u);
130 recv_length = recvmsg(fd, &msg, flags);
134 /* Here we try to retrieve destination IP and memorize it */
135 for (cmsgptr = CMSG_FIRSTHDR(&msg);
137 cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)
139 if (cmsgptr->cmsg_level == IPPROTO_IP
140 && cmsgptr->cmsg_type == IP_PKTINFO
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; */
149 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
150 if (cmsgptr->cmsg_level == IPPROTO_IPV6
151 && cmsgptr->cmsg_type == IPV6_PKTINFO
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; */