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