1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Generic non-forking server infrastructure.
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4 | * Intended to make writing telnetd-type servers easier.
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5 | *
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6 | * Copyright (C) 2007 Denis Vlasenko
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7 | *
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8 | * Licensed under GPL version 2, see file LICENSE in this tarball for details.
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9 | */
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10 |
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11 | #include "libbb.h"
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12 | #include "isrv.h"
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13 |
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14 | #define DEBUG 0
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15 |
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16 | #if DEBUG
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17 | #define DPRINTF(args...) bb_error_msg(args)
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18 | #else
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19 | #define DPRINTF(args...) ((void)0)
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20 | #endif
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21 |
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22 | /* Helpers */
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23 |
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24 | /* Opaque structure */
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25 |
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26 | struct isrv_state_t {
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27 | short *fd2peer; /* one per registered fd */
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28 | void **param_tbl; /* one per registered peer */
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29 | /* one per registered peer; doesn't exist if !timeout */
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30 | time_t *timeo_tbl;
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31 | int (*new_peer)(isrv_state_t *state, int fd);
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32 | time_t curtime;
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33 | int timeout;
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34 | int fd_count;
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35 | int peer_count;
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36 | int wr_count;
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37 | fd_set rd;
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38 | fd_set wr;
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39 | };
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40 | #define FD2PEER (state->fd2peer)
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41 | #define PARAM_TBL (state->param_tbl)
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42 | #define TIMEO_TBL (state->timeo_tbl)
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43 | #define CURTIME (state->curtime)
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44 | #define TIMEOUT (state->timeout)
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45 | #define FD_COUNT (state->fd_count)
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46 | #define PEER_COUNT (state->peer_count)
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47 | #define WR_COUNT (state->wr_count)
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48 |
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49 | /* callback */
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50 | void isrv_want_rd(isrv_state_t *state, int fd)
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51 | {
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52 | FD_SET(fd, &state->rd);
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53 | }
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54 |
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55 | /* callback */
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56 | void isrv_want_wr(isrv_state_t *state, int fd)
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57 | {
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58 | if (!FD_ISSET(fd, &state->wr)) {
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59 | WR_COUNT++;
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60 | FD_SET(fd, &state->wr);
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61 | }
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62 | }
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63 |
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64 | /* callback */
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65 | void isrv_dont_want_rd(isrv_state_t *state, int fd)
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66 | {
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67 | FD_CLR(fd, &state->rd);
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68 | }
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69 |
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70 | /* callback */
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71 | void isrv_dont_want_wr(isrv_state_t *state, int fd)
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72 | {
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73 | if (FD_ISSET(fd, &state->wr)) {
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74 | WR_COUNT--;
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75 | FD_CLR(fd, &state->wr);
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76 | }
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77 | }
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78 |
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79 | /* callback */
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80 | int isrv_register_fd(isrv_state_t *state, int peer, int fd)
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81 | {
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82 | int n;
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83 |
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84 | DPRINTF("register_fd(peer:%d,fd:%d)", peer, fd);
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85 |
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86 | if (FD_COUNT >= FD_SETSIZE) return -1;
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87 | if (FD_COUNT <= fd) {
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88 | n = FD_COUNT;
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89 | FD_COUNT = fd + 1;
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90 |
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91 | DPRINTF("register_fd: FD_COUNT %d", FD_COUNT);
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92 |
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93 | FD2PEER = xrealloc(FD2PEER, FD_COUNT * sizeof(FD2PEER[0]));
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94 | while (n < fd) FD2PEER[n++] = -1;
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95 | }
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96 |
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97 | DPRINTF("register_fd: FD2PEER[%d] = %d", fd, peer);
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98 |
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99 | FD2PEER[fd] = peer;
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100 | return 0;
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101 | }
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102 |
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103 | /* callback */
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104 | void isrv_close_fd(isrv_state_t *state, int fd)
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105 | {
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106 | DPRINTF("close_fd(%d)", fd);
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107 |
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108 | close(fd);
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109 | isrv_dont_want_rd(state, fd);
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110 | if (WR_COUNT) isrv_dont_want_wr(state, fd);
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111 |
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112 | FD2PEER[fd] = -1;
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113 | if (fd == FD_COUNT-1) {
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114 | do fd--; while (fd >= 0 && FD2PEER[fd] == -1);
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115 | FD_COUNT = fd + 1;
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116 |
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117 | DPRINTF("close_fd: FD_COUNT %d", FD_COUNT);
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118 |
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119 | FD2PEER = xrealloc(FD2PEER, FD_COUNT * sizeof(FD2PEER[0]));
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120 | }
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121 | }
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122 |
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123 | /* callback */
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124 | int isrv_register_peer(isrv_state_t *state, void *param)
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125 | {
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126 | int n;
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127 |
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128 | if (PEER_COUNT >= FD_SETSIZE) return -1;
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129 | n = PEER_COUNT++;
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130 |
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131 | DPRINTF("register_peer: PEER_COUNT %d", PEER_COUNT);
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132 |
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133 | PARAM_TBL = xrealloc(PARAM_TBL, PEER_COUNT * sizeof(PARAM_TBL[0]));
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134 | PARAM_TBL[n] = param;
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135 | if (TIMEOUT) {
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136 | TIMEO_TBL = xrealloc(TIMEO_TBL, PEER_COUNT * sizeof(TIMEO_TBL[0]));
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137 | TIMEO_TBL[n] = CURTIME;
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138 | }
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139 | return n;
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140 | }
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141 |
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142 | static void remove_peer(isrv_state_t *state, int peer)
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143 | {
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144 | int movesize;
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145 | int fd;
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146 |
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147 | DPRINTF("remove_peer(%d)", peer);
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148 |
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149 | fd = FD_COUNT - 1;
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150 | while (fd >= 0) {
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151 | if (FD2PEER[fd] == peer) {
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152 | isrv_close_fd(state, fd);
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153 | fd--;
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154 | continue;
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155 | }
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156 | if (FD2PEER[fd] > peer)
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157 | FD2PEER[fd]--;
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158 | fd--;
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159 | }
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160 |
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161 | PEER_COUNT--;
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162 | DPRINTF("remove_peer: PEER_COUNT %d", PEER_COUNT);
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163 |
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164 | movesize = (PEER_COUNT - peer) * sizeof(void*);
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165 | if (movesize > 0) {
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166 | memcpy(&PARAM_TBL[peer], &PARAM_TBL[peer+1], movesize);
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167 | if (TIMEOUT)
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168 | memcpy(&TIMEO_TBL[peer], &TIMEO_TBL[peer+1], movesize);
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169 | }
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170 | PARAM_TBL = xrealloc(PARAM_TBL, PEER_COUNT * sizeof(PARAM_TBL[0]));
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171 | if (TIMEOUT)
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172 | TIMEO_TBL = xrealloc(TIMEO_TBL, PEER_COUNT * sizeof(TIMEO_TBL[0]));
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173 | }
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174 |
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175 | static void handle_accept(isrv_state_t *state, int fd)
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176 | {
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177 | int n, newfd;
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178 |
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179 | /* suppress gcc warning "cast from ptr to int of different size" */
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180 | fcntl(fd, F_SETFL, (int)(ptrdiff_t)(PARAM_TBL[0]) | O_NONBLOCK);
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181 | newfd = accept(fd, NULL, 0);
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182 | fcntl(fd, F_SETFL, (int)(ptrdiff_t)(PARAM_TBL[0]));
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183 | if (newfd < 0) {
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184 | if (errno == EAGAIN) return;
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185 | /* Most probably someone gave us wrong fd type
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186 | * (for example, non-socket). Don't want
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187 | * to loop forever. */
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188 | bb_perror_msg_and_die("accept");
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189 | }
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190 |
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191 | DPRINTF("new_peer(%d)", newfd);
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192 | n = state->new_peer(state, newfd);
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193 | if (n)
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194 | remove_peer(state, n); /* unsuccesful peer start */
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195 | }
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196 |
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197 | void BUG_sizeof_fd_set_is_strange(void);
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198 | static void handle_fd_set(isrv_state_t *state, fd_set *fds, int (*h)(int, void **))
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199 | {
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200 | enum { LONG_CNT = sizeof(fd_set) / sizeof(long) };
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201 | int fds_pos;
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202 | int fd, peer;
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203 | /* need to know value at _the beginning_ of this routine */
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204 | int fd_cnt = FD_COUNT;
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205 |
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206 | if (LONG_CNT * sizeof(long) != sizeof(fd_set))
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207 | BUG_sizeof_fd_set_is_strange();
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208 |
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209 | fds_pos = 0;
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210 | while (1) {
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211 | /* Find next nonzero bit */
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212 | while (fds_pos < LONG_CNT) {
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213 | if (((long*)fds)[fds_pos] == 0) {
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214 | fds_pos++;
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215 | continue;
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216 | }
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217 | /* Found non-zero word */
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218 | fd = fds_pos * sizeof(long)*8; /* word# -> bit# */
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219 | while (1) {
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220 | if (FD_ISSET(fd, fds)) {
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221 | FD_CLR(fd, fds);
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222 | goto found_fd;
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223 | }
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224 | fd++;
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225 | }
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226 | }
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227 | break; /* all words are zero */
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228 | found_fd:
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229 | if (fd >= fd_cnt) { /* paranoia */
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230 | DPRINTF("handle_fd_set: fd > fd_cnt?? (%d > %d)",
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231 | fd, fd_cnt);
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232 | break;
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233 | }
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234 | DPRINTF("handle_fd_set: fd %d is active", fd);
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235 | peer = FD2PEER[fd];
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236 | if (peer < 0)
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237 | continue; /* peer is already gone */
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238 | if (peer == 0) {
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239 | handle_accept(state, fd);
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240 | continue;
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241 | }
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242 | DPRINTF("h(fd:%d)", fd);
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243 | if (h(fd, &PARAM_TBL[peer])) {
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244 | /* this peer is gone */
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245 | remove_peer(state, peer);
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246 | } else if (TIMEOUT) {
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247 | TIMEO_TBL[peer] = monotonic_sec();
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248 | }
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249 | }
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250 | }
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251 |
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252 | static void handle_timeout(isrv_state_t *state, int (*do_timeout)(void **))
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253 | {
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254 | int n, peer;
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255 | peer = PEER_COUNT-1;
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256 | /* peer 0 is not checked */
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257 | while (peer > 0) {
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258 | DPRINTF("peer %d: time diff %d", peer,
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259 | (int)(CURTIME - TIMEO_TBL[peer]));
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260 | if ((CURTIME - TIMEO_TBL[peer]) >= TIMEOUT) {
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261 | DPRINTF("peer %d: do_timeout()", peer);
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262 | n = do_timeout(&PARAM_TBL[peer]);
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263 | if (n)
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264 | remove_peer(state, peer);
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265 | }
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266 | peer--;
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267 | }
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268 | }
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269 |
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270 | /* Driver */
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271 | void isrv_run(
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272 | int listen_fd,
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273 | int (*new_peer)(isrv_state_t *state, int fd),
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274 | int (*do_rd)(int fd, void **),
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275 | int (*do_wr)(int fd, void **),
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276 | int (*do_timeout)(void **),
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277 | int timeout,
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278 | int linger_timeout)
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279 | {
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280 | isrv_state_t *state = xzalloc(sizeof(*state));
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281 | state->new_peer = new_peer;
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282 | state->timeout = timeout;
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283 |
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284 | /* register "peer" #0 - it will accept new connections */
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285 | isrv_register_peer(state, NULL);
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286 | isrv_register_fd(state, /*peer:*/ 0, listen_fd);
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287 | isrv_want_rd(state, listen_fd);
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288 | /* remember flags to make blocking<->nonblocking switch faster */
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289 | /* (suppress gcc warning "cast from ptr to int of different size") */
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290 | PARAM_TBL[0] = (void*)(ptrdiff_t)(fcntl(listen_fd, F_GETFL));
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291 |
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292 | while (1) {
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293 | struct timeval tv;
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294 | fd_set rd;
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295 | fd_set wr;
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296 | fd_set *wrp = NULL;
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297 | int n;
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298 |
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299 | tv.tv_sec = timeout;
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300 | if (PEER_COUNT <= 1)
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301 | tv.tv_sec = linger_timeout;
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302 | tv.tv_usec = 0;
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303 | rd = state->rd;
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304 | if (WR_COUNT) {
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305 | wr = state->wr;
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306 | wrp = ≀
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307 | }
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308 |
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309 | DPRINTF("run: select(FD_COUNT:%d,timeout:%d)...",
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310 | FD_COUNT, (int)tv.tv_sec);
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311 | n = select(FD_COUNT, &rd, wrp, NULL, tv.tv_sec ? &tv : NULL);
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312 | DPRINTF("run: ...select:%d", n);
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313 |
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314 | if (n < 0) {
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315 | if (errno != EINTR)
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316 | bb_perror_msg("select");
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317 | continue;
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318 | }
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319 |
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320 | if (n == 0 && linger_timeout && PEER_COUNT <= 1)
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321 | break;
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322 |
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323 | if (timeout) {
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324 | time_t t = monotonic_sec();
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325 | if (t != CURTIME) {
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326 | CURTIME = t;
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327 | handle_timeout(state, do_timeout);
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328 | }
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329 | }
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330 | if (n > 0) {
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331 | handle_fd_set(state, &rd, do_rd);
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332 | if (wrp)
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333 | handle_fd_set(state, wrp, do_wr);
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334 | }
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335 | }
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336 | DPRINTF("run: bailout");
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337 | /* NB: accept socket is not closed. Caller is to decide what to do */
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338 | }
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