/*      $NetBSD: tftp.c,v 1.4 1997/09/17 16:57:07 drochner Exp $         */

/*
 * Copyright (c) 1996
 *      Matthias Drochner.  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.
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed for the NetBSD Project
 *      by Matthias Drochner.
 * 4. 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>

/*
 * Simple TFTP implementation for libsa.
 * Assumes:
 *  - socket descriptor (int) at dev->d_opendata, dev stored at
 *      open_file->f_devdata
 *  - server host IP in global rootip
 * Restrictions:
 *  - read only
 *  - lseek only with SEEK_SET or SEEK_CUR
 *  - no big time differences between transfers (<tftp timeout)
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <netinet/udp.h>
#include <netinet/in_systm.h>
#include <arpa/tftp.h>

#include <string.h>

#include "stand.h"
#include "net.h"
#include "netif.h"

#include "tftp.h"

struct tftp_handle;
struct tftprecv_extra;

static ssize_t recvtftp(struct iodesc *, void **, void **, time_t, void *);
static int tftp_open(const char *, struct open_file *);
static int tftp_close(struct open_file *);
static int tftp_parse_oack(struct tftp_handle *, char *, size_t);
static int tftp_read(struct open_file *, void *, size_t, size_t *);
static off_t tftp_seek(struct open_file *, off_t, int);
static int tftp_set_blksize(struct tftp_handle *, const char *);
static int tftp_stat(struct open_file *, struct stat *);

struct fs_ops tftp_fsops = {
        .fs_name = "tftp",
        .fo_open = tftp_open,
        .fo_close = tftp_close,
        .fo_read = tftp_read,
        .fo_write = null_write,
        .fo_seek = tftp_seek,
        .fo_stat = tftp_stat,
        .fo_readdir = null_readdir
};

static int      tftpport = 2000;
static int      is_open = 0;

/*
 * The legacy TFTP_BLKSIZE value was SEGSIZE(512).
 * TFTP_REQUESTED_BLKSIZE of 1428 is (Ethernet MTU, less the TFTP, UDP and
 * IP header lengths).
 */
#define TFTP_REQUESTED_BLKSIZE 1428

/*
 * Choose a blksize big enough so we can test with Ethernet
 * Jumbo frames in the future.
 */
#define TFTP_MAX_BLKSIZE 9008

struct tftp_handle {
        struct iodesc  *iodesc;
        int             currblock;      /* contents of lastdata */
        int             islastblock;    /* flag */
        int             validsize;
        int             off;
        char            *path;  /* saved for re-requests */
        unsigned int    tftp_blksize;
        unsigned long   tftp_tsize;
        void            *pkt;
        struct tftphdr  *tftp_hdr;
};

struct tftprecv_extra {
        struct tftp_handle      *tftp_handle;
        unsigned short          rtype;          /* Received type */
};

#define TFTP_MAX_ERRCODE EOPTNEG
static const int tftperrors[TFTP_MAX_ERRCODE + 1] = {
        0,                      /* ??? */
        ENOENT,
        EPERM,
        ENOSPC,
        EINVAL,                 /* ??? */
        EINVAL,                 /* ??? */
        EEXIST,
        EINVAL,                 /* ??? */
        EINVAL,                 /* Option negotiation failed. */
};

static int  tftp_getnextblock(struct tftp_handle *h);

/* send error message back. */
static void
tftp_senderr(struct tftp_handle *h, ushort_t errcode, const char *msg)
{
        struct {
                uchar_t header[HEADER_SIZE];
                struct tftphdr t;
                uchar_t space[63]; /* +1 from t */
        } __packed __aligned(4) wbuf;
        char *wtail;
        int len;

        len = strlen(msg);
        if (len > sizeof (wbuf.space))
                len = sizeof (wbuf.space);

        wbuf.t.th_opcode = htons((ushort_t)ERROR);
        wbuf.t.th_code = htons(errcode);

        wtail = wbuf.t.th_msg;
        bcopy(msg, wtail, len);
        wtail[len] = '\0';
        wtail += len + 1;

        sendudp(h->iodesc, &wbuf.t, wtail - (char *)&wbuf.t);
}

static void
tftp_sendack(struct tftp_handle *h, ushort_t block)
{
        struct {
                uchar_t header[HEADER_SIZE];
                struct tftphdr  t;
        } __packed __aligned(4) wbuf;
        char *wtail;

        wbuf.t.th_opcode = htons((ushort_t)ACK);
        wtail = (char *)&wbuf.t.th_block;
        wbuf.t.th_block = htons(block);
        wtail += 2;

        sendudp(h->iodesc, &wbuf.t, wtail - (char *)&wbuf.t);
}

static ssize_t
recvtftp(struct iodesc *d, void **pkt, void **payload, time_t tleft,
    void *recv_extra)
{
        struct tftprecv_extra *extra;
        struct tftp_handle *h;
        struct tftphdr *t;
        void *ptr = NULL;
        ssize_t len;

        errno = 0;
        extra = recv_extra;
        h = extra->tftp_handle;

        len = readudp(d, &ptr, (void **)&t, tleft);

        if (len < 4) {
                free(ptr);
                return (-1);
        }

        extra->rtype = ntohs(t->th_opcode);
        switch (ntohs(t->th_opcode)) {
        case DATA: {
                int got;

                if (htons(t->th_block) < (ushort_t)d->xid) {
                        /*
                         * Apparently our ACK was missed, re-send.
                         */
                        tftp_sendack(h, htons(t->th_block));
                        free(ptr);
                        return (-1);
                }
                if (htons(t->th_block) != (ushort_t)d->xid) {
                        /*
                         * Packet from the future, drop this.
                         */
                        free(ptr);
                        return (-1);
                }
                if (d->xid == 1) {
                        /*
                         * First data packet from new port.
                         */
                        struct udphdr *uh;
                        uh = (struct udphdr *)t - 1;
                        d->destport = uh->uh_sport;
                }
                got = len - (t->th_data - (char *)t);
                *pkt = ptr;
                *payload = t;
                return (got);
        }
        case ERROR:
                if ((unsigned)ntohs(t->th_code) > TFTP_MAX_ERRCODE) {
                        printf("illegal tftp error %d\n", ntohs(t->th_code));
                        errno = EIO;
                } else {
#ifdef TFTP_DEBUG
                        printf("tftp-error %d\n", ntohs(t->th_code));
#endif
                        errno = tftperrors[ntohs(t->th_code)];
                }
                free(ptr);
                return (-1);
        case OACK: {
                struct udphdr *uh;
                int tftp_oack_len;

                /*
                 * Unexpected OACK. TFTP transfer already in progress.
                 * Drop the pkt.
                 */
                if (d->xid != 1) {
                        free(ptr);
                        return (-1);
                }

                /*
                 * Remember which port this OACK came from, because we need
                 * to send the ACK or errors back to it.
                 */
                uh = (struct udphdr *)t - 1;
                d->destport = uh->uh_sport;

                /* Parse options ACK-ed by the server. */
                tftp_oack_len = len - sizeof (t->th_opcode);
                if (tftp_parse_oack(h, t->th_u.tu_stuff, tftp_oack_len) != 0) {
                        tftp_senderr(h, EOPTNEG, "Malformed OACK");
                        errno = EIO;
                        free(ptr);
                        return (-1);
                }
                *pkt = ptr;
                *payload = t;
                return (0);
        }
        default:
#ifdef TFTP_DEBUG
                printf("tftp type %d not handled\n", ntohs(t->th_opcode));
#endif
                free(ptr);
                return (-1);
        }
}

/* send request, expect first block (or error) */
static int
tftp_makereq(struct tftp_handle *h)
{
        struct {
                uchar_t header[HEADER_SIZE];
                struct tftphdr  t;
                uchar_t space[FNAME_SIZE + 6];
        } __packed __aligned(4) wbuf;
        struct tftprecv_extra recv_extra;
        char *wtail;
        int l;
        ssize_t res;
        void *pkt;
        struct tftphdr *t;
        char *tftp_blksize = NULL;
        int blksize_l;

        /*
         * Allow overriding default TFTP block size by setting
         * a tftp.blksize environment variable.
         */
        if ((tftp_blksize = getenv("tftp.blksize")) != NULL) {
                tftp_set_blksize(h, tftp_blksize);
        }

        wbuf.t.th_opcode = htons((ushort_t)RRQ);
        wtail = wbuf.t.th_stuff;
        l = strlen(h->path);
#ifdef TFTP_PREPEND_PATH
        if (l > FNAME_SIZE - (sizeof (TFTP_PREPEND_PATH) - 1))
                return (ENAMETOOLONG);
        bcopy(TFTP_PREPEND_PATH, wtail, sizeof (TFTP_PREPEND_PATH) - 1);
        wtail += sizeof (TFTP_PREPEND_PATH) - 1;
#else
        if (l > FNAME_SIZE)
                return (ENAMETOOLONG);
#endif
        bcopy(h->path, wtail, l + 1);
        wtail += l + 1;
        bcopy("octet", wtail, 6);
        wtail += 6;
        bcopy("blksize", wtail, 8);
        wtail += 8;
        blksize_l = sprintf(wtail, "%d", h->tftp_blksize);
        wtail += blksize_l + 1;
        bcopy("tsize", wtail, 6);
        wtail += 6;
        bcopy("0", wtail, 2);
        wtail += 2;

        h->iodesc->myport = htons(tftpport + (getsecs() & 0x3ff));
        h->iodesc->destport = htons(IPPORT_TFTP);
        h->iodesc->xid = 1;     /* expected block */

        h->currblock = 0;
        h->islastblock = 0;
        h->validsize = 0;

        pkt = NULL;
        recv_extra.tftp_handle = h;
        res = sendrecv(h->iodesc, &sendudp, &wbuf.t, wtail - (char *)&wbuf.t,
            &recvtftp, &pkt, (void **)&t, &recv_extra);
        if (res == -1) {
                free(pkt);
                return (errno);
        }

        free(h->pkt);
        h->pkt = pkt;
        h->tftp_hdr = t;

        if (recv_extra.rtype == OACK)
                return (tftp_getnextblock(h));

        /* Server ignored our blksize request, revert to TFTP default. */
        h->tftp_blksize = SEGSIZE;

        switch (recv_extra.rtype) {
                case DATA: {
                        h->currblock = 1;
                        h->validsize = res;
                        h->islastblock = 0;
                        if (res < h->tftp_blksize) {
                                h->islastblock = 1;     /* very short file */
                                tftp_sendack(h, h->currblock);
                        }
                        return (0);
                }
                case ERROR:
                default:
                        return (errno);
        }

}

/* ack block, expect next */
static int
tftp_getnextblock(struct tftp_handle *h)
{
        struct {
                uchar_t header[HEADER_SIZE];
                struct tftphdr t;
        } __packed __aligned(4) wbuf;
        struct tftprecv_extra recv_extra;
        char *wtail;
        int res;
        void *pkt;
        struct tftphdr *t;

        wbuf.t.th_opcode = htons((ushort_t)ACK);
        wtail = (char *)&wbuf.t.th_block;
        wbuf.t.th_block = htons((ushort_t)h->currblock);
        wtail += 2;

        h->iodesc->xid = h->currblock + 1;      /* expected block */

        pkt = NULL;
        recv_extra.tftp_handle = h;
        res = sendrecv(h->iodesc, &sendudp, &wbuf.t, wtail - (char *)&wbuf.t,
            &recvtftp, &pkt, (void **)&t, &recv_extra);

        if (res == -1) {                /* 0 is OK! */
                free(pkt);
                return (errno);
        }

        free(h->pkt);
        h->pkt = pkt;
        h->tftp_hdr = t;
        h->currblock++;
        h->validsize = res;
        if (res < h->tftp_blksize)
                h->islastblock = 1;     /* EOF */

        if (h->islastblock == 1) {
                /* Send an ACK for the last block */
                wbuf.t.th_block = htons((ushort_t)h->currblock);
                sendudp(h->iodesc, &wbuf.t, wtail - (char *)&wbuf.t);
        }

        return (0);
}

static int
tftp_open(const char *path, struct open_file *f)
{
        struct devdesc *dev;
        struct tftp_handle *tftpfile;
        struct iodesc   *io;
        int             res;
        const char      *extraslash;

        if (netproto != NET_TFTP)
                return (EINVAL);

        if (f->f_dev->dv_type != DEVT_NET)
                return (EINVAL);

        if (is_open)
                return (EBUSY);

        tftpfile = calloc(1, sizeof (*tftpfile));
        if (!tftpfile)
                return (ENOMEM);

        tftpfile->tftp_blksize = TFTP_REQUESTED_BLKSIZE;
        dev = f->f_devdata;
        tftpfile->iodesc = io = socktodesc(*(int *)(dev->d_opendata));
        if (io == NULL) {
                free(tftpfile);
                return (EINVAL);
        }

        io->destip = rootip;
        tftpfile->off = 0;

        /*
         * Remove leading '/' from path, because we will append it to
         * rootpath.
         */
        while (path[0] == '/')
                path++;

        /* tftp does not support reading directories */
        if (path[0] == '\0' || path[strlen(path) - 1] == '/')
                return (EPERM);

        if (rootpath[strlen(rootpath) - 1] == '/') {
                extraslash = "";
        } else {
                extraslash = "/";
        }

        res = asprintf(&tftpfile->path, "%s%s%s", rootpath, extraslash, path);
        if (res < 0) {
                free(tftpfile);
                return (ENOMEM);
        }

        res = tftp_makereq(tftpfile);
        if (res) {
                free(tftpfile->path);
                free(tftpfile->pkt);
                free(tftpfile);
                return (res);
        }
        f->f_fsdata = tftpfile;
        is_open = 1;
        return (0);
}

static int
tftp_read(struct open_file *f, void *addr, size_t size,
    size_t *resid /* out */)
{
        struct tftp_handle *tftpfile;
        size_t res;
        int rc;

        rc = 0;
        res = size;
        tftpfile = f->f_fsdata;

        /* Make sure we will not read past file end */
        if (tftpfile->tftp_tsize > 0 &&
            tftpfile->off + size > tftpfile->tftp_tsize) {
                size = tftpfile->tftp_tsize - tftpfile->off;
        }

        while (size > 0) {
                int needblock, count;

                twiddle(32);

                needblock = tftpfile->off / tftpfile->tftp_blksize + 1;

                if (tftpfile->currblock > needblock) {  /* seek backwards */
                        tftp_senderr(tftpfile, 0, "No error: read aborted");
                        rc = tftp_makereq(tftpfile);
                        if (rc != 0)
                                break;
                }

                while (tftpfile->currblock < needblock) {

                        rc = tftp_getnextblock(tftpfile);
                        if (rc) {       /* no answer */
#ifdef TFTP_DEBUG
                                printf("tftp: read error\n");
#endif
                                return (rc);
                        }
                        if (tftpfile->islastblock)
                                break;
                }

                if (tftpfile->currblock == needblock) {
                        int offinblock, inbuffer;

                        offinblock = tftpfile->off % tftpfile->tftp_blksize;

                        inbuffer = tftpfile->validsize - offinblock;
                        if (inbuffer < 0) {
#ifdef TFTP_DEBUG
                                printf("tftp: invalid offset %d\n",
                                    tftpfile->off);
#endif
                                return (EINVAL);
                        }
                        count = (size < inbuffer ? size : inbuffer);
                        bcopy(tftpfile->tftp_hdr->th_data + offinblock,
                            addr, count);

                        addr = (char *)addr + count;
                        tftpfile->off += count;
                        size -= count;
                        res -= count;

                        if ((tftpfile->islastblock) && (count == inbuffer))
                                break;  /* EOF */
                } else {
#ifdef TFTP_DEBUG
                        printf("tftp: block %d not found\n", needblock);
#endif
                        return (EINVAL);
                }

        }

        if (resid != NULL)
                *resid = res;
        return (rc);
}

static int
tftp_close(struct open_file *f)
{
        struct tftp_handle *tftpfile;
        tftpfile = f->f_fsdata;

        /* let it time out ... */

        if (tftpfile) {
                free(tftpfile->path);
                free(tftpfile->pkt);
                free(tftpfile);
        }
        is_open = 0;
        return (0);
}

static int
tftp_stat(struct open_file *f, struct stat *sb)
{
        struct tftp_handle *tftpfile;
        tftpfile = f->f_fsdata;

        sb->st_mode = 0444 | S_IFREG;
        sb->st_nlink = 1;
        sb->st_uid = 0;
        sb->st_gid = 0;
        sb->st_size = tftpfile->tftp_tsize;
        return (0);
}

static off_t
tftp_seek(struct open_file *f, off_t offset, int where)
{
        struct tftp_handle *tftpfile;
        tftpfile = f->f_fsdata;

        switch (where) {
        case SEEK_SET:
                tftpfile->off = offset;
                break;
        case SEEK_CUR:
                tftpfile->off += offset;
                break;
        default:
                errno = EOFFSET;
                return (-1);
        }
        return (tftpfile->off);
}

static int
tftp_set_blksize(struct tftp_handle *h, const char *str)
{
        char *endptr;
        int new_blksize;
        int ret = 0;

        if (h == NULL || str == NULL)
                return (ret);

        new_blksize =
            (unsigned int)strtol(str, &endptr, 0);

        /*
         * Only accept blksize value if it is numeric.
         * RFC2348 specifies that acceptable values are 8-65464.
         * Let's choose a limit less than MAXRSPACE.
         */
        if (*endptr == '\0' && new_blksize >= 8 &&
            new_blksize <= TFTP_MAX_BLKSIZE) {
                h->tftp_blksize = new_blksize;
                ret = 1;
        }

        return (ret);
}

/*
 * In RFC2347, the TFTP Option Acknowledgement package (OACK)
 * is used to acknowledge a client's option negotiation request.
 * The format of an OACK packet is:
 *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
 *    |  opc  |  opt1  | 0 | value1 | 0 |  optN  | 0 | valueN | 0 |
 *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
 *
 *    opc
 *       The opcode field contains a 6, for Option Acknowledgment.
 *
 *    opt1
 *       The first option acknowledgment, copied from the original
 *       request.
 *
 *    value1
 *       The acknowledged value associated with the first option.  If
 *       and how this value may differ from the original request is
 *       detailed in the specification for the option.
 *
 *    optN, valueN
 *       The final option/value acknowledgment pair.
 */
static int
tftp_parse_oack(struct tftp_handle *h, char *buf, size_t len)
{
        /*
         *  We parse the OACK strings into an array
         *  of name-value pairs.
         */
        char *tftp_options[128] = { 0 };
        char *val = buf;
        int i = 0;
        int option_idx = 0;
        int blksize_is_set = 0;
        int tsize = 0;

        unsigned int orig_blksize;

        while (option_idx < 128 && i < len) {
                if (buf[i] == '\0') {
                        if (&buf[i] > val) {
                                tftp_options[option_idx] = val;
                                val = &buf[i] + 1;
                                ++option_idx;
                        }
                }
                ++i;
        }

        /* Save the block size we requested for sanity check later. */
        orig_blksize = h->tftp_blksize;

        /*
         * Parse individual TFTP options.
         *    * "blksize" is specified in RFC2348.
         *    * "tsize" is specified in RFC2349.
         */
        for (i = 0; i < option_idx; i += 2) {
                if (strcasecmp(tftp_options[i], "blksize") == 0) {
                        if (i + 1 < option_idx)
                                blksize_is_set =
                                    tftp_set_blksize(h, tftp_options[i + 1]);
                } else if (strcasecmp(tftp_options[i], "tsize") == 0) {
                        if (i + 1 < option_idx)
                                tsize = strtol(tftp_options[i + 1], NULL, 10);
                        if (tsize != 0)
                                h->tftp_tsize = tsize;
                } else {
                        /*
                         * Do not allow any options we did not expect to be
                         * ACKed.
                         */
                        printf("unexpected tftp option '%s'\n",
                            tftp_options[i]);
                        return (-1);
                }
        }

        if (!blksize_is_set) {
                /*
                 * If TFTP blksize was not set, try defaulting
                 * to the legacy TFTP blksize of SEGSIZE(512)
                 */
                h->tftp_blksize = SEGSIZE;
        } else if (h->tftp_blksize > orig_blksize) {
                /*
                 * Server should not be proposing block sizes that
                 * exceed what we said we can handle.
                 */
                printf("unexpected blksize %u\n", h->tftp_blksize);
                return (-1);
        }

#ifdef TFTP_DEBUG
        printf("tftp_blksize: %u\n", h->tftp_blksize);
        printf("tftp_tsize: %lu\n", h->tftp_tsize);
#endif
        return (0);
}