/*-
 * SPDX-License-Identifier: (BSD-3-Clause AND Beerware)
 *
 * Copyright (c) 1998-2011 Dag-Erling Smørgrav
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
/*
 * Portions of this code were taken from or based on ftpio.c:
 *
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <phk@FreeBSD.org> wrote this file.  As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
 * ----------------------------------------------------------------------------
 *
 * Major Changelog:
 *
 * Dag-Erling Smørgrav
 * 9 Jun 1998
 *
 * Incorporated into libfetch
 *
 * Jordan K. Hubbard
 * 17 Jan 1996
 *
 * Turned inside out. Now returns xfers as new file ids, not as a special
 * `state' of FTP_t
 *
 * $ftpioId: ftpio.c,v 1.30 1998/04/11 07:28:53 phk Exp $
 *
 */

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "fetch.h"
#include "common.h"
#include "ftperr.h"

#define FTP_ANONYMOUS_USER      "anonymous"

#define FTP_CONNECTION_ALREADY_OPEN     125
#define FTP_OPEN_DATA_CONNECTION        150
#define FTP_OK                          200
#define FTP_FILE_STATUS                 213
#define FTP_SERVICE_READY               220
#define FTP_TRANSFER_COMPLETE           226
#define FTP_PASSIVE_MODE                227
#define FTP_LPASSIVE_MODE               228
#define FTP_EPASSIVE_MODE               229
#define FTP_LOGGED_IN                   230
#define FTP_FILE_ACTION_OK              250
#define FTP_DIRECTORY_CREATED           257 /* multiple meanings */
#define FTP_FILE_CREATED                257 /* multiple meanings */
#define FTP_WORKING_DIRECTORY           257 /* multiple meanings */
#define FTP_NEED_PASSWORD               331
#define FTP_NEED_ACCOUNT                332
#define FTP_FILE_OK                     350
#define FTP_SYNTAX_ERROR                500
#define FTP_PROTOCOL_ERROR              999

static struct url cached_host;
static conn_t   *cached_connection;

#define isftpreply(foo)                         \
        (isdigit((unsigned char)foo[0]) &&      \
            isdigit((unsigned char)foo[1]) &&   \
            isdigit((unsigned char)foo[2]) &&   \
            (foo[3] == ' ' || foo[3] == '\0'))
#define isftpinfo(foo) \
        (isdigit((unsigned char)foo[0]) &&      \
            isdigit((unsigned char)foo[1]) &&   \
            isdigit((unsigned char)foo[2]) &&   \
            foo[3] == '-')

/*
 * Translate IPv4 mapped IPv6 address to IPv4 address
 */
static void
unmappedaddr(struct sockaddr_in6 *sin6)
{
        struct sockaddr_in *sin4;
        u_int32_t addr;
        int port;

        if (sin6->sin6_family != AF_INET6 ||
            !IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr))
                return;
        sin4 = (struct sockaddr_in *)sin6;
        addr = *(u_int32_t *)(uintptr_t)&sin6->sin6_addr.s6_addr[12];
        port = sin6->sin6_port;
        memset(sin4, 0, sizeof(struct sockaddr_in));
        sin4->sin_addr.s_addr = addr;
        sin4->sin_port = port;
        sin4->sin_family = AF_INET;
        sin4->sin_len = sizeof(struct sockaddr_in);
}

/*
 * Get server response
 */
static int
ftp_chkerr(conn_t *conn)
{
        if (fetch_getln(conn) == -1) {
                fetch_syserr();
                return (-1);
        }
        if (isftpinfo(conn->buf)) {
                while (conn->buflen && !isftpreply(conn->buf)) {
                        if (fetch_getln(conn) == -1) {
                                fetch_syserr();
                                return (-1);
                        }
                }
        }

        while (conn->buflen &&
            isspace((unsigned char)conn->buf[conn->buflen - 1]))
                conn->buflen--;
        conn->buf[conn->buflen] = '\0';

        if (!isftpreply(conn->buf)) {
                ftp_seterr(FTP_PROTOCOL_ERROR);
                return (-1);
        }

        conn->err = (conn->buf[0] - '0') * 100
            + (conn->buf[1] - '0') * 10
            + (conn->buf[2] - '0');

        return (conn->err);
}

/*
 * Send a command and check reply
 */
static int
ftp_cmd(conn_t *conn, const char *fmt, ...)
{
        va_list ap;
        size_t len;
        char *msg;
        int r;

        va_start(ap, fmt);
        len = vasprintf(&msg, fmt, ap);
        va_end(ap);

        if (msg == NULL) {
                errno = ENOMEM;
                fetch_syserr();
                return (-1);
        }

        r = fetch_putln(conn, msg, len);
        free(msg);

        if (r == -1) {
                fetch_syserr();
                return (-1);
        }

        return (ftp_chkerr(conn));
}

/*
 * Return a pointer to the filename part of a path
 */
static const char *
ftp_filename(const char *file, int *len, int *type)
{
        const char *s;

        if ((s = strrchr(file, '/')) == NULL)
                s = file;
        else
                s = s + 1;
        *len = strlen(s);
        if (*len > 7 && strncmp(s + *len - 7, ";type=", 6) == 0) {
                *type = s[*len - 1];
                *len -= 7;
        } else {
                *type = '\0';
        }
        return (s);
}

/*
 * Get current working directory from the reply to a CWD, PWD or CDUP
 * command.
 */
static int
ftp_pwd(conn_t *conn, char *pwd, size_t pwdlen)
{
        char *src, *dst, *end;
        int q;

        if (conn->err != FTP_WORKING_DIRECTORY &&
            conn->err != FTP_FILE_ACTION_OK)
                return (FTP_PROTOCOL_ERROR);
        end = conn->buf + conn->buflen;
        src = conn->buf + 4;
        if (src >= end || *src++ != '"')
                return (FTP_PROTOCOL_ERROR);
        for (q = 0, dst = pwd; src < end && pwdlen--; ++src) {
                if (!q && *src == '"')
                        q = 1;
                else if (q && *src != '"')
                        break;
                else if (q)
                        *dst++ = '"', q = 0;
                else
                        *dst++ = *src;
        }
        if (!pwdlen)
                return (FTP_PROTOCOL_ERROR);
        *dst = '\0';
#if 0
        DEBUGF("pwd: [%s]\n", pwd);
#endif
        return (FTP_OK);
}

/*
 * Change working directory to the directory that contains the specified
 * file.
 */
static int
ftp_cwd(conn_t *conn, const char *file)
{
        const char *beg, *end;
        char pwd[PATH_MAX];
        int e, i, len;

        /* If no slashes in name, no need to change dirs. */
        if ((end = strrchr(file, '/')) == NULL)
                return (0);
        if ((e = ftp_cmd(conn, "PWD")) != FTP_WORKING_DIRECTORY ||
            (e = ftp_pwd(conn, pwd, sizeof(pwd))) != FTP_OK) {
                ftp_seterr(e);
                return (-1);
        }
        for (;;) {
                len = strlen(pwd);

                /* Look for a common prefix between PWD and dir to fetch. */
                for (i = 0; i <= len && i <= end - file; ++i)
                        if (pwd[i] != file[i])
                                break;
#if 0
                DEBUGF("have: [%.*s|%s]\n", i, pwd, pwd + i);
                DEBUGF("want: [%.*s|%s]\n", i, file, file + i);
#endif
                /* Keep going up a dir until we have a matching prefix. */
                if (pwd[i] == '\0' && (file[i - 1] == '/' || file[i] == '/'))
                        break;
                if ((e = ftp_cmd(conn, "CDUP")) != FTP_FILE_ACTION_OK ||
                    (e = ftp_cmd(conn, "PWD")) != FTP_WORKING_DIRECTORY ||
                    (e = ftp_pwd(conn, pwd, sizeof(pwd))) != FTP_OK) {
                        ftp_seterr(e);
                        return (-1);
                }
        }

#ifdef FTP_COMBINE_CWDS
        /* Skip leading slashes, even "////". */
        for (beg = file + i; beg < end && *beg == '/'; ++beg, ++i)
                /* nothing */ ;

        /* If there is no trailing dir, we're already there. */
        if (beg >= end)
                return (0);

        /* Change to the directory all in one chunk (e.g., foo/bar/baz). */
        e = ftp_cmd(conn, "CWD %.*s", (int)(end - beg), beg);
        if (e == FTP_FILE_ACTION_OK)
                return (0);
#endif /* FTP_COMBINE_CWDS */

        /* That didn't work so go back to legacy behavior (multiple CWDs). */
        for (beg = file + i; beg < end; beg = file + i + 1) {
                while (*beg == '/')
                        ++beg, ++i;
                for (++i; file + i < end && file[i] != '/'; ++i)
                        /* nothing */ ;
                e = ftp_cmd(conn, "CWD %.*s", file + i - beg, beg);
                if (e != FTP_FILE_ACTION_OK) {
                        ftp_seterr(e);
                        return (-1);
                }
        }
        return (0);
}

/*
 * Set transfer mode and data type
 */
static int
ftp_mode_type(conn_t *conn, int mode, int type)
{
        int e;

        switch (mode) {
        case 0:
        case 's':
                mode = 'S';
        case 'S':
                break;
        default:
                return (FTP_PROTOCOL_ERROR);
        }
        if ((e = ftp_cmd(conn, "MODE %c", mode)) != FTP_OK) {
                if (mode == 'S') {
                        /*
                         * Stream mode is supposed to be the default - so
                         * much so that some servers not only do not
                         * support any other mode, but do not support the
                         * MODE command at all.
                         *
                         * If "MODE S" fails, it is unlikely that we
                         * previously succeeded in setting a different
                         * mode.  Therefore, we simply hope that the
                         * server is already in the correct mode, and
                         * silently ignore the failure.
                         */
                } else {
                        return (e);
                }
        }

        switch (type) {
        case 0:
        case 'i':
                type = 'I';
        case 'I':
                break;
        case 'a':
                type = 'A';
        case 'A':
                break;
        case 'd':
                type = 'D';
        case 'D':
                /* can't handle yet */
        default:
                return (FTP_PROTOCOL_ERROR);
        }
        if ((e = ftp_cmd(conn, "TYPE %c", type)) != FTP_OK)
                return (e);

        return (FTP_OK);
}

/*
 * Request and parse file stats
 */
static int
ftp_stat(conn_t *conn, const char *file, struct url_stat *us)
{
        char *ln;
        const char *filename;
        int filenamelen, type;
        struct tm tm;
        time_t t;
        int e;

        us->size = -1;
        us->atime = us->mtime = 0;

        filename = ftp_filename(file, &filenamelen, &type);

        if ((e = ftp_mode_type(conn, 0, type)) != FTP_OK) {
                ftp_seterr(e);
                return (-1);
        }

        e = ftp_cmd(conn, "SIZE %.*s", filenamelen, filename);
        if (e != FTP_FILE_STATUS) {
                ftp_seterr(e);
                return (-1);
        }
        for (ln = conn->buf + 4; *ln && isspace((unsigned char)*ln); ln++)
                /* nothing */ ;
        for (us->size = 0; *ln && isdigit((unsigned char)*ln); ln++)
                us->size = us->size * 10 + *ln - '0';
        if (*ln && !isspace((unsigned char)*ln)) {
                ftp_seterr(FTP_PROTOCOL_ERROR);
                us->size = -1;
                return (-1);
        }
        if (us->size == 0)
                us->size = -1;
        DEBUGF("size: [%lld]\n", (long long)us->size);

        e = ftp_cmd(conn, "MDTM %.*s", filenamelen, filename);
        if (e != FTP_FILE_STATUS) {
                ftp_seterr(e);
                return (-1);
        }
        for (ln = conn->buf + 4; *ln && isspace((unsigned char)*ln); ln++)
                /* nothing */ ;
        switch (strspn(ln, "0123456789")) {
        case 14:
                break;
        case 15:
                ln++;
                ln[0] = '2';
                ln[1] = '0';
                break;
        default:
                ftp_seterr(FTP_PROTOCOL_ERROR);
                return (-1);
        }
        if (sscanf(ln, "%04d%02d%02d%02d%02d%02d",
            &tm.tm_year, &tm.tm_mon, &tm.tm_mday,
            &tm.tm_hour, &tm.tm_min, &tm.tm_sec) != 6) {
                ftp_seterr(FTP_PROTOCOL_ERROR);
                return (-1);
        }
        tm.tm_mon--;
        tm.tm_year -= 1900;
        tm.tm_isdst = -1;
        t = timegm(&tm);
        if (t == (time_t)-1)
                t = time(NULL);
        us->mtime = t;
        us->atime = t;
        DEBUGF("last modified: [%04d-%02d-%02d %02d:%02d:%02d]\n",
            tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
            tm.tm_hour, tm.tm_min, tm.tm_sec);
        return (0);
}

/*
 * I/O functions for FTP
 */
struct ftpio {
        conn_t  *cconn;         /* Control connection */
        conn_t  *dconn;         /* Data connection */
        int      dir;           /* Direction */
        int      eof;           /* EOF reached */
        int      err;           /* Error code */
};

static int       ftp_readfn(void *, char *, int);
static int       ftp_writefn(void *, const char *, int);
static fpos_t    ftp_seekfn(void *, fpos_t, int);
static int       ftp_closefn(void *);

static int
ftp_readfn(void *v, char *buf, int len)
{
        struct ftpio *io;
        int r;

        io = (struct ftpio *)v;
        if (io == NULL) {
                errno = EBADF;
                return (-1);
        }
        if (io->cconn == NULL || io->dconn == NULL || io->dir == O_WRONLY) {
                errno = EBADF;
                return (-1);
        }
        if (io->err) {
                errno = io->err;
                return (-1);
        }
        if (io->eof)
                return (0);
        r = fetch_read(io->dconn, buf, len);
        if (r > 0)
                return (r);
        if (r == 0) {
                io->eof = 1;
                return (0);
        }
        if (errno != EINTR)
                io->err = errno;
        return (-1);
}

static int
ftp_writefn(void *v, const char *buf, int len)
{
        struct ftpio *io;
        int w;

        io = (struct ftpio *)v;
        if (io == NULL) {
                errno = EBADF;
                return (-1);
        }
        if (io->cconn == NULL || io->dconn == NULL || io->dir == O_RDONLY) {
                errno = EBADF;
                return (-1);
        }
        if (io->err) {
                errno = io->err;
                return (-1);
        }
        w = fetch_write(io->dconn, buf, len);
        if (w >= 0)
                return (w);
        if (errno != EINTR)
                io->err = errno;
        return (-1);
}

static fpos_t
ftp_seekfn(void *v, fpos_t pos __unused, int whence __unused)
{
        struct ftpio *io;

        io = (struct ftpio *)v;
        if (io == NULL) {
                errno = EBADF;
                return (-1);
        }
        errno = ESPIPE;
        return (-1);
}

static int
ftp_closefn(void *v)
{
        struct ftpio *io;
        int r;

        io = (struct ftpio *)v;
        if (io == NULL) {
                errno = EBADF;
                return (-1);
        }
        if (io->dir == -1)
                return (0);
        if (io->cconn == NULL || io->dconn == NULL) {
                errno = EBADF;
                return (-1);
        }
        fetch_close(io->dconn);
        io->dir = -1;
        io->dconn = NULL;
        DEBUGF("Waiting for final status\n");
        r = ftp_chkerr(io->cconn);
        if (io->cconn == cached_connection && io->cconn->ref == 1)
                cached_connection = NULL;
        fetch_close(io->cconn);
        free(io);
        return (r == FTP_TRANSFER_COMPLETE) ? 0 : -1;
}

static FILE *
ftp_setup(conn_t *cconn, conn_t *dconn, int mode)
{
        struct ftpio *io;
        FILE *f;

        if (cconn == NULL || dconn == NULL)
                return (NULL);
        if ((io = malloc(sizeof(*io))) == NULL)
                return (NULL);
        io->cconn = cconn;
        io->dconn = dconn;
        io->dir = mode;
        io->eof = io->err = 0;
        f = funopen(io, ftp_readfn, ftp_writefn, ftp_seekfn, ftp_closefn);
        if (f == NULL)
                free(io);
        return (f);
}

/*
 * Transfer file
 */
static FILE *
ftp_transfer(conn_t *conn, const char *oper, const char *file,
    int mode, off_t offset, const char *flags)
{
        struct sockaddr_storage sa;
        struct sockaddr_in6 *sin6;
        struct sockaddr_in *sin4;
        const char *bindaddr;
        const char *filename;
        int filenamelen, type;
        int low, pasv, verbose;
        int e, sd = -1;
        socklen_t l;
        char *s;
        FILE *df;

        /* check flags */
        low = CHECK_FLAG('l');
        pasv = CHECK_FLAG('p') || !CHECK_FLAG('P');
        verbose = CHECK_FLAG('v');

        /* passive mode */
        if ((s = getenv("FTP_PASSIVE_MODE")) != NULL)
                pasv = (strncasecmp(s, "no", 2) != 0);

        /* isolate filename */
        filename = ftp_filename(file, &filenamelen, &type);

        /* set transfer mode and data type */
        if ((e = ftp_mode_type(conn, 0, type)) != FTP_OK)
                goto ouch;

        /* find our own address, bind, and listen */
        l = sizeof(sa);
        if (getsockname(conn->sd, (struct sockaddr *)&sa, &l) == -1)
                goto sysouch;
        if (sa.ss_family == AF_INET6)
                unmappedaddr((struct sockaddr_in6 *)&sa);

        /* open data socket */
        if ((sd = socket(sa.ss_family, SOCK_STREAM, IPPROTO_TCP)) == -1) {
                fetch_syserr();
                return (NULL);
        }

        if (pasv) {
                u_char addr[64];
                char *ln, *p;
                unsigned int i;
                int port;

                /* send PASV command */
                if (verbose)
                        fetch_info("setting passive mode");
                switch (sa.ss_family) {
                case AF_INET:
                        if ((e = ftp_cmd(conn, "PASV")) != FTP_PASSIVE_MODE)
                                goto ouch;
                        break;
                case AF_INET6:
                        if ((e = ftp_cmd(conn, "EPSV")) != FTP_EPASSIVE_MODE) {
                                if (e == -1)
                                        goto ouch;
                                if ((e = ftp_cmd(conn, "LPSV")) !=
                                    FTP_LPASSIVE_MODE)
                                        goto ouch;
                        }
                        break;
                default:
                        e = FTP_PROTOCOL_ERROR; /* XXX: error code should be prepared */
                        goto ouch;
                }

                /*
                 * Find address and port number. The reply to the PASV command
                 * is IMHO the one and only weak point in the FTP protocol.
                 */
                ln = conn->buf;
                switch (e) {
                case FTP_PASSIVE_MODE:
                case FTP_LPASSIVE_MODE:
                        for (p = ln + 3; *p && !isdigit((unsigned char)*p); p++)
                                /* nothing */ ;
                        if (!*p) {
                                e = FTP_PROTOCOL_ERROR;
                                goto ouch;
                        }
                        l = (e == FTP_PASSIVE_MODE ? 6 : 21);
                        for (i = 0; *p && i < l; i++, p++) {
                                addr[i] = strtol(p, &p, 10);
                                if (*p == '\0' && i < l - 1)
                                        break;
                        }
                        if (i < l) {
                                e = FTP_PROTOCOL_ERROR;
                                goto ouch;
                        }
                        break;
                case FTP_EPASSIVE_MODE:
                        for (p = ln + 3; *p && *p != '('; p++)
                                /* nothing */ ;
                        if (!*p) {
                                e = FTP_PROTOCOL_ERROR;
                                goto ouch;
                        }
                        ++p;
                        if (sscanf(p, "%c%c%c%d%c", &addr[0], &addr[1], &addr[2],
                                &port, &addr[3]) != 5 ||
                            addr[0] != addr[1] ||
                            addr[0] != addr[2] || addr[0] != addr[3]) {
                                e = FTP_PROTOCOL_ERROR;
                                goto ouch;
                        }
                        break;
                }

                /* seek to required offset */
                if (offset)
                        if (ftp_cmd(conn, "REST %lu", (u_long)offset) != FTP_FILE_OK)
                                goto sysouch;

                /* construct sockaddr for data socket */
                l = sizeof(sa);
                if (getpeername(conn->sd, (struct sockaddr *)&sa, &l) == -1)
                        goto sysouch;
                if (sa.ss_family == AF_INET6)
                        unmappedaddr((struct sockaddr_in6 *)&sa);
                switch (sa.ss_family) {
                case AF_INET6:
                        sin6 = (struct sockaddr_in6 *)&sa;
                        if (e == FTP_EPASSIVE_MODE)
                                sin6->sin6_port = htons(port);
                        else {
                                memcpy(&sin6->sin6_addr, addr + 2, 16);
                                memcpy(&sin6->sin6_port, addr + 19, 2);
                        }
                        break;
                case AF_INET:
                        sin4 = (struct sockaddr_in *)&sa;
                        if (e == FTP_EPASSIVE_MODE)
                                sin4->sin_port = htons(port);
                        else {
                                memcpy(&sin4->sin_addr, addr, 4);
                                memcpy(&sin4->sin_port, addr + 4, 2);
                        }
                        break;
                default:
                        e = FTP_PROTOCOL_ERROR; /* XXX: error code should be prepared */
                        break;
                }

                /* connect to data port */
                if (verbose)
                        fetch_info("opening data connection");
                bindaddr = getenv("FETCH_BIND_ADDRESS");
                if (bindaddr != NULL && *bindaddr != '\0' &&
                    (e = fetch_bind(sd, sa.ss_family, bindaddr)) != 0)
                        goto ouch;
                if (connect(sd, (struct sockaddr *)&sa, sa.ss_len) == -1)
                        goto sysouch;

                /* make the server initiate the transfer */
                if (verbose)
                        fetch_info("initiating transfer");
                e = ftp_cmd(conn, "%s %.*s", oper, filenamelen, filename);
                if (e != FTP_CONNECTION_ALREADY_OPEN && e != FTP_OPEN_DATA_CONNECTION)
                        goto ouch;

        } else {
                u_int32_t a;
                u_short p;
                int arg, d;
                char *ap;
                char hname[INET6_ADDRSTRLEN];

                switch (sa.ss_family) {
                case AF_INET6:
                        ((struct sockaddr_in6 *)&sa)->sin6_port = 0;
#ifdef IPV6_PORTRANGE
                        arg = low ? IPV6_PORTRANGE_DEFAULT : IPV6_PORTRANGE_HIGH;
                        if (setsockopt(sd, IPPROTO_IPV6, IPV6_PORTRANGE,
                                (char *)&arg, sizeof(arg)) == -1)
                                goto sysouch;
#endif
                        break;
                case AF_INET:
                        ((struct sockaddr_in *)&sa)->sin_port = 0;
                        arg = low ? IP_PORTRANGE_DEFAULT : IP_PORTRANGE_HIGH;
                        if (setsockopt(sd, IPPROTO_IP, IP_PORTRANGE,
                                (char *)&arg, sizeof(arg)) == -1)
                                goto sysouch;
                        break;
                }
                if (verbose)
                        fetch_info("binding data socket");
                if (bind(sd, (struct sockaddr *)&sa, sa.ss_len) == -1)
                        goto sysouch;
                if (listen(sd, 1) == -1)
                        goto sysouch;

                /* find what port we're on and tell the server */
                if (getsockname(sd, (struct sockaddr *)&sa, &l) == -1)
                        goto sysouch;
                switch (sa.ss_family) {
                case AF_INET:
                        sin4 = (struct sockaddr_in *)&sa;
                        a = ntohl(sin4->sin_addr.s_addr);
                        p = ntohs(sin4->sin_port);
                        e = ftp_cmd(conn, "PORT %d,%d,%d,%d,%d,%d",
                            (a >> 24) & 0xff, (a >> 16) & 0xff,
                            (a >> 8) & 0xff, a & 0xff,
                            (p >> 8) & 0xff, p & 0xff);
                        break;
                case AF_INET6:
#define UC(b)   (((int)b)&0xff)
                        e = -1;
                        sin6 = (struct sockaddr_in6 *)&sa;
                        sin6->sin6_scope_id = 0;
                        if (getnameinfo((struct sockaddr *)&sa, sa.ss_len,
                                hname, sizeof(hname),
                                NULL, 0, NI_NUMERICHOST) == 0) {
                                e = ftp_cmd(conn, "EPRT |%d|%s|%d|", 2, hname,
                                    htons(sin6->sin6_port));
                                if (e == -1)
                                        goto ouch;
                        }
                        if (e != FTP_OK) {
                                ap = (char *)&sin6->sin6_addr;
                                e = ftp_cmd(conn,
                                    "LPRT %d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d",
                                    6, 16,
                                    UC(ap[0]), UC(ap[1]), UC(ap[2]), UC(ap[3]),
                                    UC(ap[4]), UC(ap[5]), UC(ap[6]), UC(ap[7]),
                                    UC(ap[8]), UC(ap[9]), UC(ap[10]), UC(ap[11]),
                                    UC(ap[12]), UC(ap[13]), UC(ap[14]), UC(ap[15]),
                                    2,
                                    (ntohs(sin6->sin6_port) >> 8) & 0xff,
                                    ntohs(sin6->sin6_port)        & 0xff);
                        }
                        break;
                default:
                        e = FTP_PROTOCOL_ERROR; /* XXX: error code should be prepared */
                        goto ouch;
                }
                if (e != FTP_OK)
                        goto ouch;

                /* seek to required offset */
                if (offset)
                        if (ftp_cmd(conn, "REST %ju", (uintmax_t)offset) != FTP_FILE_OK)
                                goto sysouch;

                /* make the server initiate the transfer */
                if (verbose)
                        fetch_info("initiating transfer");
                e = ftp_cmd(conn, "%s %.*s", oper, filenamelen, filename);
                if (e != FTP_CONNECTION_ALREADY_OPEN && e != FTP_OPEN_DATA_CONNECTION)
                        goto ouch;

                /* accept the incoming connection and go to town */
                if ((d = accept(sd, NULL, NULL)) == -1)
                        goto sysouch;
                close(sd);
                sd = d;
        }

        if ((df = ftp_setup(conn, fetch_reopen(sd), mode)) == NULL)
                goto sysouch;
        return (df);

sysouch:
        fetch_syserr();
        if (sd >= 0)
                close(sd);
        return (NULL);

ouch:
        if (e != -1)
                ftp_seterr(e);
        if (sd >= 0)
                close(sd);
        return (NULL);
}

/*
 * Authenticate
 */
static int
ftp_authenticate(conn_t *conn, struct url *url, struct url *purl)
{
        const char *user, *pwd, *logname;
        char pbuf[MAXHOSTNAMELEN + MAXLOGNAME + 1];
        int e, len;

        /* XXX FTP_AUTH, and maybe .netrc */

        /* send user name and password */
        if (url->user[0] == '\0')
                fetch_netrc_auth(url);
        user = url->user;
        if (*user == '\0')
                if ((user = getenv("FTP_LOGIN")) != NULL)
                        DEBUGF("FTP_LOGIN=%s\n", user);
        if (user == NULL || *user == '\0')
                user = FTP_ANONYMOUS_USER;
        if (purl && url->port == fetch_default_port(url->scheme))
                e = ftp_cmd(conn, "USER %s@%s", user, url->host);
        else if (purl)
                e = ftp_cmd(conn, "USER %s@%s@%d", user, url->host, url->port);
        else
                e = ftp_cmd(conn, "USER %s", user);

        /* did the server request a password? */
        if (e == FTP_NEED_PASSWORD) {
                pwd = url->pwd;
                if (*pwd == '\0')
                        if ((pwd = getenv("FTP_PASSWORD")) != NULL)
                                DEBUGF("FTP_PASSWORD=%s\n", pwd);
                if (pwd == NULL || *pwd == '\0') {
                        if ((logname = getlogin()) == NULL)
                                logname = FTP_ANONYMOUS_USER;
                        if ((len = snprintf(pbuf, MAXLOGNAME + 1, "%s@", logname)) < 0)
                                len = 0;
                        else if (len > MAXLOGNAME)
                                len = MAXLOGNAME;
                        gethostname(pbuf + len, sizeof(pbuf) - len);
                        pwd = pbuf;
                }
                e = ftp_cmd(conn, "PASS %s", pwd);
        }

        return (e);
}

/*
 * Log on to FTP server
 */
static conn_t *
ftp_connect(struct url *url, struct url *purl, const char *flags)
{
        conn_t *conn;
        int e, direct, verbose;
#ifdef INET6
        int af = AF_UNSPEC;
#else
        int af = AF_INET;
#endif

        direct = CHECK_FLAG('d');
        verbose = CHECK_FLAG('v');
        if (CHECK_FLAG('4'))
                af = AF_INET;
        else if (CHECK_FLAG('6'))
                af = AF_INET6;

        if (direct)
                purl = NULL;

        /* check for proxy */
        if (purl) {
                /* XXX proxy authentication! */
                conn = fetch_connect(purl->host, purl->port, af, verbose);
        } else {
                /* no proxy, go straight to target */
                conn = fetch_connect(url->host, url->port, af, verbose);
                purl = NULL;
        }

        /* check connection */
        if (conn == NULL)
                /* fetch_connect() has already set an error code */
                return (NULL);

        /* expect welcome message */
        if ((e = ftp_chkerr(conn)) != FTP_SERVICE_READY)
                goto fouch;

        /* authenticate */
        if ((e = ftp_authenticate(conn, url, purl)) != FTP_LOGGED_IN)
                goto fouch;

        /* TODO: Request extended features supported, if any (RFC 3659). */

        /* done */
        return (conn);

fouch:
        if (e != -1)
                ftp_seterr(e);
        fetch_close(conn);
        return (NULL);
}

/*
 * Disconnect from server
 */
static void
ftp_disconnect(conn_t *conn)
{
        (void)ftp_cmd(conn, "QUIT");
        if (conn == cached_connection && conn->ref == 1)
                cached_connection = NULL;
        fetch_close(conn);
}

/*
 * Check if we're already connected
 */
static int
ftp_isconnected(struct url *url)
{
        return (cached_connection
            && (strcmp(url->host, cached_host.host) == 0)
            && (strcmp(url->user, cached_host.user) == 0)
            && (strcmp(url->pwd, cached_host.pwd) == 0)
            && (url->port == cached_host.port));
}

/*
 * Check the cache, reconnect if no luck
 */
static conn_t *
ftp_cached_connect(struct url *url, struct url *purl, const char *flags)
{
        conn_t *conn;
        int e;

        /* set default port */
        if (!url->port)
                url->port = fetch_default_port(url->scheme);

        /* try to use previously cached connection */
        if (ftp_isconnected(url)) {
                e = ftp_cmd(cached_connection, "NOOP");
                if (e == FTP_OK || e == FTP_SYNTAX_ERROR)
                        return (fetch_ref(cached_connection));
        }

        /* connect to server */
        if ((conn = ftp_connect(url, purl, flags)) == NULL)
                return (NULL);
        if (cached_connection)
                ftp_disconnect(cached_connection);
        cached_connection = fetch_ref(conn);
        memcpy(&cached_host, url, sizeof(*url));
        return (conn);
}

/*
 * Check the proxy settings
 */
static struct url *
ftp_get_proxy(struct url * url, const char *flags)
{
        struct url *purl;
        char *p;

        if (flags != NULL && strchr(flags, 'd') != NULL)
                return (NULL);
        if (fetch_no_proxy_match(url->host))
                return (NULL);
        if (((p = getenv("FTP_PROXY")) || (p = getenv("ftp_proxy")) ||
                (p = getenv("HTTP_PROXY")) || (p = getenv("http_proxy"))) &&
            *p && (purl = fetchParseURL(p)) != NULL) {
                if (!*purl->scheme) {
                        if (getenv("FTP_PROXY") || getenv("ftp_proxy"))
                                strcpy(purl->scheme, SCHEME_FTP);
                        else
                                strcpy(purl->scheme, SCHEME_HTTP);
                }
                if (!purl->port)
                        purl->port = fetch_default_proxy_port(purl->scheme);
                if (strcmp(purl->scheme, SCHEME_FTP) == 0 ||
                    strcmp(purl->scheme, SCHEME_HTTP) == 0)
                        return (purl);
                fetchFreeURL(purl);
        }
        return (NULL);
}

/*
 * Process an FTP request
 */
FILE *
ftp_request(struct url *url, const char *op, struct url_stat *us,
    struct url *purl, const char *flags)
{
        conn_t *conn;
        int oflag;

        /* check if we should use HTTP instead */
        if (purl && (strcmp(purl->scheme, SCHEME_HTTP) == 0 ||
            strcmp(purl->scheme, SCHEME_HTTPS) == 0)) {
                if (strcmp(op, "STAT") == 0)
                        return (http_request(url, "HEAD", us, purl, flags));
                else if (strcmp(op, "RETR") == 0)
                        return (http_request(url, "GET", us, purl, flags));
                /*
                 * Our HTTP code doesn't support PUT requests yet, so try
                 * a direct connection.
                 */
        }

        /* connect to server */
        conn = ftp_cached_connect(url, purl, flags);
        if (purl)
                fetchFreeURL(purl);
        if (conn == NULL)
                return (NULL);

        /* change directory */
        if (ftp_cwd(conn, url->doc) == -1)
                goto errsock;

        /* stat file */
        if (us && ftp_stat(conn, url->doc, us) == -1
            && fetchLastErrCode != FETCH_PROTO
            && fetchLastErrCode != FETCH_UNAVAIL)
                goto errsock;

        /* just a stat */
        if (strcmp(op, "STAT") == 0) {
                --conn->ref;
                ftp_disconnect(conn);
                return (FILE *)1; /* bogus return value */
        }
        if (strcmp(op, "STOR") == 0 || strcmp(op, "APPE") == 0)
                oflag = O_WRONLY;
        else
                oflag = O_RDONLY;

        /* initiate the transfer */
        return (ftp_transfer(conn, op, url->doc, oflag, url->offset, flags));

errsock:
        ftp_disconnect(conn);
        return (NULL);
}

/*
 * Get and stat file
 */
FILE *
fetchXGetFTP(struct url *url, struct url_stat *us, const char *flags)
{
        return (ftp_request(url, "RETR", us, ftp_get_proxy(url, flags), flags));
}

/*
 * Get file
 */
FILE *
fetchGetFTP(struct url *url, const char *flags)
{
        return (fetchXGetFTP(url, NULL, flags));
}

/*
 * Put file
 */
FILE *
fetchPutFTP(struct url *url, const char *flags)
{
        return (ftp_request(url, CHECK_FLAG('a') ? "APPE" : "STOR", NULL,
            ftp_get_proxy(url, flags), flags));
}

/*
 * Get file stats
 */
int
fetchStatFTP(struct url *url, struct url_stat *us, const char *flags)
{
        FILE *f;

        f = ftp_request(url, "STAT", us, ftp_get_proxy(url, flags), flags);
        if (f == NULL)
                return (-1);
        /*
         * When op is "STAT", ftp_request() will return either NULL or
         * (FILE *)1, never a valid FILE *, so we mustn't fclose(f) before
         * returning, as it would cause a segfault.
         */
        return (0);
}

/*
 * List a directory
 */
struct url_ent *
fetchListFTP(struct url *url __unused, const char *flags __unused)
{
        warnx("fetchListFTP(): not implemented");
        return (NULL);
}