src/master/dup2-array.c

/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "array.h"
#include "dup2-array.h"

#include <unistd.h>

void dup2_append(ARRAY_TYPE(dup2) *dups, int fd_src, int fd_dest)
{
    struct dup2 d;

    i_assert(fd_src >= 0);
    i_assert(fd_dest >= 0);

    d.fd_src = fd_src;
    d.fd_dest = fd_dest;
    array_append(dups, &d, 1);
}

int dup2_array(ARRAY_TYPE(dup2) *dups_arr)
{
    struct dup2 *dups;
    bool *moved, moves;
    unsigned int i, j, count, conflict;
    int fd;

    dups = array_get_modifiable(dups_arr, &count);

    moved = t_new(bool, count);
    for (;;) {
        conflict = count;
        moves = FALSE;
        for (i = 0; i < count; i++) {
            if (moved[i])
                continue;

            for (j = 0; j < count; j++) {
                if (dups[j].fd_src == dups[i].fd_dest &&
                    !moved[j]) {
                    conflict = j;
                    break;
                }
            }

            if (j == count) {
                /* no conflicts, move it */
                moved[i] = TRUE;
                moves = TRUE;
                if (dup2(dups[i].fd_src, dups[i].fd_dest) < 0) {
                    i_error("dup2(%d, %d) failed: %m",
                        dups[i].fd_src,
                        dups[i].fd_dest);
                    return -1;
                }
            }
        }
        if (conflict == count)
            break;

        if (moves) {
            /* it's possible that the conflicting fd was
               moved already. try again. */
            continue;
        }

        /* ok, we have to dup() */
        fd = dup(dups[conflict].fd_src);
        if (fd == -1) {
            i_error("dup(%d) failed: %m", dups[conflict].fd_src);
            return -1;
        }
        fd_close_on_exec(fd, TRUE);
                dups[conflict].fd_src = fd;
    }
    return 0;
}