[3320] | 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 Denys Vlasenko
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| 7 | *
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| 8 | * Licensed under GPLv2, see file LICENSE in this source tree.
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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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