busybox/networking/isrv.c

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/* vi: set sw=4 ts=4: */
/*
* Generic non-forking server infrastructure.
* Intended to make writing telnetd-type servers easier.
*
* Copyright (C) 2007 Denys Vlasenko
*
* Licensed under GPL version 2, see file LICENSE in this tarball for details.
*/
#include "libbb.h"
#include "isrv.h"
#define DEBUG 0
#if DEBUG
#define DPRINTF(args...) bb_error_msg(args)
#else
#define DPRINTF(args...) ((void)0)
#endif
/* Helpers */
/* Opaque structure */
struct isrv_state_t {
short *fd2peer; /* one per registered fd */
void **param_tbl; /* one per registered peer */
/* one per registered peer; doesn't exist if !timeout */
time_t *timeo_tbl;
int (*new_peer)(isrv_state_t *state, int fd);
time_t curtime;
int timeout;
int fd_count;
int peer_count;
int wr_count;
fd_set rd;
fd_set wr;
};
#define FD2PEER (state->fd2peer)
#define PARAM_TBL (state->param_tbl)
#define TIMEO_TBL (state->timeo_tbl)
#define CURTIME (state->curtime)
#define TIMEOUT (state->timeout)
#define FD_COUNT (state->fd_count)
#define PEER_COUNT (state->peer_count)
#define WR_COUNT (state->wr_count)
/* callback */
void isrv_want_rd(isrv_state_t *state, int fd)
{
FD_SET(fd, &state->rd);
}
/* callback */
void isrv_want_wr(isrv_state_t *state, int fd)
{
if (!FD_ISSET(fd, &state->wr)) {
WR_COUNT++;
FD_SET(fd, &state->wr);
}
}
/* callback */
void isrv_dont_want_rd(isrv_state_t *state, int fd)
{
FD_CLR(fd, &state->rd);
}
/* callback */
void isrv_dont_want_wr(isrv_state_t *state, int fd)
{
if (FD_ISSET(fd, &state->wr)) {
WR_COUNT--;
FD_CLR(fd, &state->wr);
}
}
/* callback */
int isrv_register_fd(isrv_state_t *state, int peer, int fd)
{
int n;
DPRINTF("register_fd(peer:%d,fd:%d)", peer, fd);
if (FD_COUNT >= FD_SETSIZE) return -1;
if (FD_COUNT <= fd) {
n = FD_COUNT;
FD_COUNT = fd + 1;
DPRINTF("register_fd: FD_COUNT %d", FD_COUNT);
FD2PEER = xrealloc(FD2PEER, FD_COUNT * sizeof(FD2PEER[0]));
while (n < fd) FD2PEER[n++] = -1;
}
DPRINTF("register_fd: FD2PEER[%d] = %d", fd, peer);
FD2PEER[fd] = peer;
return 0;
}
/* callback */
void isrv_close_fd(isrv_state_t *state, int fd)
{
DPRINTF("close_fd(%d)", fd);
close(fd);
isrv_dont_want_rd(state, fd);
if (WR_COUNT) isrv_dont_want_wr(state, fd);
FD2PEER[fd] = -1;
if (fd == FD_COUNT-1) {
do fd--; while (fd >= 0 && FD2PEER[fd] == -1);
FD_COUNT = fd + 1;
DPRINTF("close_fd: FD_COUNT %d", FD_COUNT);
FD2PEER = xrealloc(FD2PEER, FD_COUNT * sizeof(FD2PEER[0]));
}
}
/* callback */
int isrv_register_peer(isrv_state_t *state, void *param)
{
int n;
if (PEER_COUNT >= FD_SETSIZE) return -1;
n = PEER_COUNT++;
DPRINTF("register_peer: PEER_COUNT %d", PEER_COUNT);
PARAM_TBL = xrealloc(PARAM_TBL, PEER_COUNT * sizeof(PARAM_TBL[0]));
PARAM_TBL[n] = param;
if (TIMEOUT) {
TIMEO_TBL = xrealloc(TIMEO_TBL, PEER_COUNT * sizeof(TIMEO_TBL[0]));
TIMEO_TBL[n] = CURTIME;
}
return n;
}
static void remove_peer(isrv_state_t *state, int peer)
{
int movesize;
int fd;
DPRINTF("remove_peer(%d)", peer);
fd = FD_COUNT - 1;
while (fd >= 0) {
if (FD2PEER[fd] == peer) {
isrv_close_fd(state, fd);
fd--;
continue;
}
if (FD2PEER[fd] > peer)
FD2PEER[fd]--;
fd--;
}
PEER_COUNT--;
DPRINTF("remove_peer: PEER_COUNT %d", PEER_COUNT);
movesize = (PEER_COUNT - peer) * sizeof(void*);
if (movesize > 0) {
memcpy(&PARAM_TBL[peer], &PARAM_TBL[peer+1], movesize);
if (TIMEOUT)
memcpy(&TIMEO_TBL[peer], &TIMEO_TBL[peer+1], movesize);
}
PARAM_TBL = xrealloc(PARAM_TBL, PEER_COUNT * sizeof(PARAM_TBL[0]));
if (TIMEOUT)
TIMEO_TBL = xrealloc(TIMEO_TBL, PEER_COUNT * sizeof(TIMEO_TBL[0]));
}
static void handle_accept(isrv_state_t *state, int fd)
{
int n, newfd;
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/* suppress gcc warning "cast from ptr to int of different size" */
fcntl(fd, F_SETFL, (int)(ptrdiff_t)(PARAM_TBL[0]) | O_NONBLOCK);
newfd = accept(fd, NULL, 0);
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fcntl(fd, F_SETFL, (int)(ptrdiff_t)(PARAM_TBL[0]));
if (newfd < 0) {
if (errno == EAGAIN) return;
/* Most probably someone gave us wrong fd type
* (for example, non-socket). Don't want
* to loop forever. */
bb_perror_msg_and_die("accept");
}
DPRINTF("new_peer(%d)", newfd);
n = state->new_peer(state, newfd);
if (n)
remove_peer(state, n); /* unsuccesful peer start */
}
void BUG_sizeof_fd_set_is_strange(void);
static void handle_fd_set(isrv_state_t *state, fd_set *fds, int (*h)(int, void **))
{
enum { LONG_CNT = sizeof(fd_set) / sizeof(long) };
int fds_pos;
int fd, peer;
/* need to know value at _the beginning_ of this routine */
int fd_cnt = FD_COUNT;
if (LONG_CNT * sizeof(long) != sizeof(fd_set))
BUG_sizeof_fd_set_is_strange();
fds_pos = 0;
while (1) {
/* Find next nonzero bit */
while (fds_pos < LONG_CNT) {
if (((long*)fds)[fds_pos] == 0) {
fds_pos++;
continue;
}
/* Found non-zero word */
fd = fds_pos * sizeof(long)*8; /* word# -> bit# */
while (1) {
if (FD_ISSET(fd, fds)) {
FD_CLR(fd, fds);
goto found_fd;
}
fd++;
}
}
break; /* all words are zero */
found_fd:
if (fd >= fd_cnt) { /* paranoia */
DPRINTF("handle_fd_set: fd > fd_cnt?? (%d > %d)",
fd, fd_cnt);
break;
}
DPRINTF("handle_fd_set: fd %d is active", fd);
peer = FD2PEER[fd];
if (peer < 0)
continue; /* peer is already gone */
if (peer == 0) {
handle_accept(state, fd);
continue;
}
DPRINTF("h(fd:%d)", fd);
if (h(fd, &PARAM_TBL[peer])) {
/* this peer is gone */
remove_peer(state, peer);
} else if (TIMEOUT) {
TIMEO_TBL[peer] = monotonic_sec();
}
}
}
static void handle_timeout(isrv_state_t *state, int (*do_timeout)(void **))
{
int n, peer;
peer = PEER_COUNT-1;
/* peer 0 is not checked */
while (peer > 0) {
DPRINTF("peer %d: time diff %d", peer,
(int)(CURTIME - TIMEO_TBL[peer]));
if ((CURTIME - TIMEO_TBL[peer]) >= TIMEOUT) {
DPRINTF("peer %d: do_timeout()", peer);
n = do_timeout(&PARAM_TBL[peer]);
if (n)
remove_peer(state, peer);
}
peer--;
}
}
/* Driver */
void isrv_run(
int listen_fd,
int (*new_peer)(isrv_state_t *state, int fd),
int (*do_rd)(int fd, void **),
int (*do_wr)(int fd, void **),
int (*do_timeout)(void **),
int timeout,
int linger_timeout)
{
isrv_state_t *state = xzalloc(sizeof(*state));
state->new_peer = new_peer;
state->timeout = timeout;
/* register "peer" #0 - it will accept new connections */
isrv_register_peer(state, NULL);
isrv_register_fd(state, /*peer:*/ 0, listen_fd);
isrv_want_rd(state, listen_fd);
/* remember flags to make blocking<->nonblocking switch faster */
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/* (suppress gcc warning "cast from ptr to int of different size") */
PARAM_TBL[0] = (void*)(ptrdiff_t)(fcntl(listen_fd, F_GETFL));
while (1) {
struct timeval tv;
fd_set rd;
fd_set wr;
fd_set *wrp = NULL;
int n;
tv.tv_sec = timeout;
if (PEER_COUNT <= 1)
tv.tv_sec = linger_timeout;
tv.tv_usec = 0;
rd = state->rd;
if (WR_COUNT) {
wr = state->wr;
wrp = &wr;
}
DPRINTF("run: select(FD_COUNT:%d,timeout:%d)...",
FD_COUNT, (int)tv.tv_sec);
n = select(FD_COUNT, &rd, wrp, NULL, tv.tv_sec ? &tv : NULL);
DPRINTF("run: ...select:%d", n);
if (n < 0) {
if (errno != EINTR)
bb_perror_msg("select");
continue;
}
if (n == 0 && linger_timeout && PEER_COUNT <= 1)
break;
if (timeout) {
time_t t = monotonic_sec();
if (t != CURTIME) {
CURTIME = t;
handle_timeout(state, do_timeout);
}
}
if (n > 0) {
handle_fd_set(state, &rd, do_rd);
if (wrp)
handle_fd_set(state, wrp, do_wr);
}
}
DPRINTF("run: bailout");
/* NB: accept socket is not closed. Caller is to decide what to do */
}