/* vi: set sw=4 ts=4: */
/*
 * tiny fuser implementation
 *
 * Copyright 2004 Tony J. White
 *
 * Licensed under GPLv2, see file LICENSE in this tarball for details.
 */

#include "libbb.h"

#define MAX_LINE 255

#define OPTION_STRING "mks64"
enum {
        OPT_MOUNT  = (1 << 0),
        OPT_KILL   = (1 << 1),
        OPT_SILENT = (1 << 2),
        OPT_IP6    = (1 << 3),
        OPT_IP4    = (1 << 4),
};

typedef struct inode_list {
        struct inode_list *next;
        ino_t inode;
        dev_t dev;
} inode_list;

typedef struct pid_list {
        struct pid_list *next;
        pid_t pid;
} pid_list;

static dev_t find_socket_dev(void)
{
        int fd = socket(AF_INET, SOCK_DGRAM, 0);
        if (fd >= 0) {
                struct stat buf;
                int r = fstat(fd, &buf);
                close(fd);
                if (r == 0)
                        return buf.st_dev;
        }
        return 0;
}

static int file_to_dev_inode(const char *filename, dev_t *dev, ino_t *inode)
{
        struct stat f_stat;
        if (stat(filename, &f_stat))
                return 0;
        *inode = f_stat.st_ino;
        *dev = f_stat.st_dev;
        return 1;
}

static char *parse_net_arg(const char *arg, unsigned *port)
{
        char path[20], tproto[5];

        if (sscanf(arg, "%u/%4s", port, tproto) != 2)
                return NULL;
        sprintf(path, "/proc/net/%s", tproto);
        if (access(path, R_OK) != 0)
                return NULL;
        return xstrdup(tproto);
}

static pid_list *add_pid(pid_list *plist, pid_t pid)
{
        pid_list *curr = plist;
        while (curr != NULL) {
                if (curr->pid == pid)
                        return plist;
                curr = curr->next;
        }
        curr = xmalloc(sizeof(pid_list));
        curr->pid = pid;
        curr->next = plist;
        return curr;
}

static inode_list *add_inode(inode_list *ilist, dev_t dev, ino_t inode)
{
        inode_list *curr = ilist;
        while (curr != NULL) {
                if (curr->inode == inode && curr->dev == dev)
                        return ilist;
                curr = curr->next;
        }
        curr = xmalloc(sizeof(inode_list));
        curr->dev = dev;
        curr->inode = inode;
        curr->next = ilist;
        return curr;
}

static inode_list *scan_proc_net(const char *proto,
                                unsigned port, inode_list *ilist)
{
        char path[20], line[MAX_LINE + 1];
        ino_t tmp_inode;
        dev_t tmp_dev;
        long long uint64_inode;
        unsigned tmp_port;
        FILE *f;

        tmp_dev = find_socket_dev();

        sprintf(path, "/proc/net/%s", proto);
        f = fopen_for_read(path);
        if (!f)
                return ilist;

        while (fgets(line, MAX_LINE, f)) {
                char addr[68];
                if (sscanf(line, "%*d: %64[0-9A-Fa-f]:%x %*x:%*x %*x %*x:%*x "
                                "%*x:%*x %*x %*d %*d %llu",
                                addr, &tmp_port, &uint64_inode) == 3
                ) {
                        int len = strlen(addr);
                        if (len == 8 && (option_mask32 & OPT_IP6))
                                continue;
                        if (len > 8 && (option_mask32 & OPT_IP4))
                                continue;
                        if (tmp_port == port) {
                                tmp_inode = uint64_inode;
                                ilist = add_inode(ilist, tmp_dev, tmp_inode);
                        }
                }
        }
        fclose(f);
        return ilist;
}

static int search_dev_inode(inode_list *ilist, dev_t dev, ino_t inode)
{
        while (ilist) {
                if (ilist->dev == dev) {
                        if (option_mask32 & OPT_MOUNT)
                                return 1;
                        if (ilist->inode == inode)
                                return 1;
                }
                ilist = ilist->next;
        }
        return 0;
}

static pid_list *scan_pid_maps(const char *fname, pid_t pid,
                                inode_list *ilist, pid_list *plist)
{
        FILE *file;
        char line[MAX_LINE + 1];
        int major, minor;
        ino_t inode;
        long long uint64_inode;
        dev_t dev;

        file = fopen_for_read(fname);
        if (!file)
                return plist;
        while (fgets(line, MAX_LINE, file)) {
                if (sscanf(line, "%*s %*s %*s %x:%x %llu", &major, &minor, &uint64_inode) != 3)
                        continue;
                inode = uint64_inode;
                if (major == 0 && minor == 0 && inode == 0)
                        continue;
                dev = makedev(major, minor);
                if (search_dev_inode(ilist, dev, inode))
                        plist = add_pid(plist, pid);
        }
        fclose(file);
        return plist;
}

static pid_list *scan_link(const char *lname, pid_t pid,
                                inode_list *ilist, pid_list *plist)
{
        ino_t inode;
        dev_t dev;

        if (!file_to_dev_inode(lname, &dev, &inode))
                return plist;
        if (search_dev_inode(ilist, dev, inode))
                plist = add_pid(plist, pid);
        return plist;
}

static pid_list *scan_dir_links(const char *dname, pid_t pid,
                                inode_list *ilist, pid_list *plist)
{
        DIR *d;
        struct dirent *de;
        char *lname;

        d = opendir(dname);
        if (!d)
                return plist;
        while ((de = readdir(d)) != NULL) {
                lname = concat_subpath_file(dname, de->d_name);
                if (lname == NULL)
                        continue;
                plist = scan_link(lname, pid, ilist, plist);
                free(lname);
        }
        closedir(d);
        return plist;
}

/* NB: does chdir internally */
static pid_list *scan_proc_pids(inode_list *ilist)
{
        DIR *d;
        struct dirent *de;
        pid_t pid;
        pid_list *plist;

        xchdir("/proc");
        d = opendir("/proc");
        if (!d)
                return NULL;

        plist = NULL;
        while ((de = readdir(d)) != NULL) {
                pid = (pid_t)bb_strtou(de->d_name, NULL, 10);
                if (errno)
                        continue;
                if (chdir(de->d_name) < 0)
                        continue;
                plist = scan_link("cwd", pid, ilist, plist);
                plist = scan_link("exe", pid, ilist, plist);
                plist = scan_link("root", pid, ilist, plist);
                plist = scan_dir_links("fd", pid, ilist, plist);
                plist = scan_dir_links("lib", pid, ilist, plist);
                plist = scan_dir_links("mmap", pid, ilist, plist);
                plist = scan_pid_maps("maps", pid, ilist, plist);
                xchdir("/proc");
        }
        closedir(d);
        return plist;
}

static int print_pid_list(pid_list *plist)
{
        while (plist != NULL) {
                printf("%u ", (unsigned)plist->pid);
                plist = plist->next;
        }
        bb_putchar('\n');
        return 1;
}

static int kill_pid_list(pid_list *plist, int sig)
{
        pid_t mypid = getpid();
        int success = 1;

        while (plist != NULL) {
                if (plist->pid != mypid) {
                        if (kill(plist->pid, sig) != 0) {
                                bb_perror_msg("kill pid %u", (unsigned)plist->pid);
                                success = 0;
                        }
                }
                plist = plist->next;
        }
        return success;
}

int fuser_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int fuser_main(int argc UNUSED_PARAM, char **argv)
{
        pid_list *plist;
        inode_list *ilist;
        char **pp;
        dev_t dev;
        ino_t inode;
        unsigned port;
        int opt;
        int success;
        int killsig;
/*
fuser [options] FILEs or PORT/PROTOs
Find processes which use FILEs or PORTs
        -m      Find processes which use same fs as FILEs
        -4      Search only IPv4 space
        -6      Search only IPv6 space
        -s      Silent: just exit with 0 if any processes are found
        -k      Kill found processes (otherwise display PIDs)
        -SIGNAL Signal to send (default: TERM)
*/
        /* Handle -SIGNAL. Oh my... */
        killsig = SIGTERM;
        pp = argv;
        while (*++pp) {
                char *arg = *pp;
                if (arg[0] != '-')
                        continue;
                if (arg[1] == '-' && arg[2] == '\0') /* "--" */
                        break;
                if ((arg[1] == '4' || arg[1] == '6') && arg[2] == '\0')
                        continue; /* it's "-4" or "-6" */
                opt = get_signum(&arg[1]);
                if (opt < 0)
                        continue;
                /* "-SIGNAL" option found. Remove it and bail out */
                killsig = opt;
                do {
                        pp[0] = arg = pp[1];
                        pp++;
                } while (arg);
                break;
        }

        opt = getopt32(argv, OPTION_STRING);
        argv += optind;

        ilist = NULL;
        pp = argv;
        while (*pp) {
                char *proto = parse_net_arg(*pp, &port);
                if (proto) { /* PORT/PROTO */
                        ilist = scan_proc_net(proto, port, ilist);
                        free(proto);
                } else { /* FILE */
                        if (!file_to_dev_inode(*pp, &dev, &inode))
                                bb_perror_msg_and_die("can't open '%s'", *pp);
                        ilist = add_inode(ilist, dev, inode);
                }
                pp++;
        }

        plist = scan_proc_pids(ilist); /* changes dir to "/proc" */

        if (!plist)
                return EXIT_FAILURE;
        success = 1;
        if (opt & OPT_KILL) {
                success = kill_pid_list(plist, killsig);
        } else if (!(opt & OPT_SILENT)) {
                success = print_pid_list(plist);
        }
        return (success != 1); /* 0 == success */
}