slirp/tftp.c - emulators/simh - Rivoreo Source Code Repositories

 /*
  * tftp.c - a simple, read-only tftp server for qemu
  *
  * Copyright (c) 2004 Magnus Damm <damm@opensource.se>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 #include <slirp.h>
 #include "qemu-common.h"

 static inline int tftp_session_in_use(struct tftp_session *spt)
 {
     return (spt->slirp != NULL);
 }

 static inline void tftp_session_update(struct tftp_session *spt)
 {
     spt->timestamp = curtime;
 }

 static void tftp_session_terminate(struct tftp_session *spt)
 {
     if (spt->f != NULL) {
         fclose(spt->f);
         spt->f = NULL;
     }
     g_free(spt->filename);
     spt->slirp = NULL;
 }

 static int tftp_session_allocate(Slirp *slirp, struct tftp_t *tp)
 {
   struct tftp_session *spt;
   int k;

   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
     spt = &slirp->tftp_sessions[k];

     if (!tftp_session_in_use(spt))
         goto found;

     /* sessions time out after 5 inactive seconds */
     if ((int)(curtime - spt->timestamp) > 5000) {
         tftp_session_terminate(spt);
         goto found;
     }
   }

   return -1;

  found:
   memset(spt, 0, sizeof(*spt));
   memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
   spt->f = NULL;
   spt->client_port = tp->udp.uh_sport;
   spt->slirp = slirp;

   tftp_session_update(spt);

   return k;
 }

 static int tftp_session_find(Slirp *slirp, struct tftp_t *tp)
 {
   struct tftp_session *spt;
   int k;

   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
     spt = &slirp->tftp_sessions[k];

     if (tftp_session_in_use(spt)) {
       if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
         if (spt->client_port == tp->udp.uh_sport) {
           return k;
         }
       }
     }
   }

   return -1;
 }

 static int tftp_read_data(struct tftp_session *spt, uint32_t block_nr,
                           uint8_t *buf, int len)
 {
     int bytes_read = 0;

     if (spt->f == NULL) {
         spt->f = fopen(spt->filename, "rb");
     }

     if (spt->f == NULL) {
         return -1;
     }

     if (len) {
         fseek(spt->f, block_nr * 512, SEEK_SET);

         bytes_read = fread(buf, 1, len, spt->f);
     }

     return bytes_read;
 }

 static int tftp_send_oack(struct tftp_session *spt,
                           const char *keys[], uint32_t values[], int nb,
                           struct tftp_t *recv_tp)
 {
     struct sockaddr_in saddr, daddr;
     struct mbuf *m;
     struct tftp_t *tp;
     int i, n = 0;

     m = m_get(spt->slirp);

     if (!m)
         return -1;

     memset(m->m_data, 0, m->m_size);

     m->m_data += IF_MAXLINKHDR;
     tp = (struct tftp_t *)m->m_data;
     m->m_data += sizeof(struct udpiphdr);

     tp->tp_op = htons(TFTP_OACK);
     for (i = 0; i < nb; i++) {
         n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
                       keys[i]) + 1;
         n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
                       values[i]) + 1;
     }

     saddr.sin_addr = recv_tp->ip.ip_dst;
     saddr.sin_port = recv_tp->udp.uh_dport;

     daddr.sin_addr = spt->client_ip;
     daddr.sin_port = spt->client_port;

     m->m_len = sizeof(struct tftp_t) - 514 + n -
         sizeof(struct ip) - sizeof(struct udphdr);
     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

     return 0;
 }

 static void tftp_send_error(struct tftp_session *spt,
                             uint16_t errorcode, const char *msg,
                             struct tftp_t *recv_tp)
 {
   struct sockaddr_in saddr, daddr;
   struct mbuf *m;
   struct tftp_t *tp;

   m = m_get(spt->slirp);

   if (!m) {
     goto out;
   }

   memset(m->m_data, 0, m->m_size);

   m->m_data += IF_MAXLINKHDR;
   tp = (struct tftp_t *)m->m_data;
   m->m_data += sizeof(struct udpiphdr);

   tp->tp_op = htons(TFTP_ERROR);
   tp->x.tp_error.tp_error_code = htons(errorcode);
   pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);

   saddr.sin_addr = recv_tp->ip.ip_dst;
   saddr.sin_port = recv_tp->udp.uh_dport;

   daddr.sin_addr = spt->client_ip;
   daddr.sin_port = spt->client_port;

   m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
         sizeof(struct ip) - sizeof(struct udphdr);

   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

 out:
   tftp_session_terminate(spt);
 }

 static void tftp_send_next_block(struct tftp_session *spt,
                                  struct tftp_t *recv_tp)
 {
   struct sockaddr_in saddr, daddr;
   struct mbuf *m;
   struct tftp_t *tp;
   int nobytes;

   m = m_get(spt->slirp);

   if (!m) {
     return;
   }

   memset(m->m_data, 0, m->m_size);

   m->m_data += IF_MAXLINKHDR;
   tp = (struct tftp_t *)m->m_data;
   m->m_data += sizeof(struct udpiphdr);

   tp->tp_op = htons(TFTP_DATA);
   tp->x.tp_data.tp_block_nr = htons((spt->block_nr + 1) & 0xffff);

   saddr.sin_addr = recv_tp->ip.ip_dst;
   saddr.sin_port = recv_tp->udp.uh_dport;

   daddr.sin_addr = spt->client_ip;
   daddr.sin_port = spt->client_port;

   nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf, 512);

   if (nobytes < 0) {
     m_free(m);

     /* send "file not found" error back */

     tftp_send_error(spt, 1, "File not found", tp);

     return;
   }

   m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
         sizeof(struct ip) - sizeof(struct udphdr);

   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

   if (nobytes == 512) {
     tftp_session_update(spt);
   }
   else {
     tftp_session_terminate(spt);
   }

   spt->block_nr++;
 }

 static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
 {
   struct tftp_session *spt;
   int s, k;
   size_t prefix_len;
   char *req_fname;
   const char *option_name[2];
   uint32_t option_value[2];
   int nb_options = 0;

   /* check if a session already exists and if so terminate it */
   s = tftp_session_find(slirp, tp);
   if (s >= 0) {
     tftp_session_terminate(&slirp->tftp_sessions[s]);
   }

   s = tftp_session_allocate(slirp, tp);

   if (s < 0) {
     return;
   }

   spt = &slirp->tftp_sessions[s];

   /* unspecified prefix means service disabled */
   if (!slirp->tftp_prefix) {
       tftp_send_error(spt, 2, "Access violation", tp);
       return;
   }

   /* skip header fields */
   k = 0;
   pktlen -= offsetof(struct tftp_t, x.tp_buf);

   /* prepend tftp_prefix */
   prefix_len = strlen(slirp->tftp_prefix);
   spt->filename = (char *)g_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
   memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
   spt->filename[prefix_len] = '/';

   /* get name */
   req_fname = spt->filename + prefix_len + 1;

   while (1) {
     if (k >= TFTP_FILENAME_MAX || k >= pktlen) {
       tftp_send_error(spt, 2, "Access violation", tp);
       return;
     }
     req_fname[k] = tp->x.tp_buf[k];
     if (req_fname[k++] == '\0') {
       break;
     }
   }

   /* check mode */
   if ((pktlen - k) < 6) {
     tftp_send_error(spt, 2, "Access violation", tp);
     return;
   }

   if (strcasecmp(&tp->x.tp_buf[k], "octet") != 0) {
       tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
       return;
   }

   k += 6; /* skipping octet */

   /* do sanity checks on the filename */
   if (!strncmp(req_fname, "../", 3) ||
       req_fname[strlen(req_fname) - 1] == '/' ||
       strstr(req_fname, "/../")) {
       tftp_send_error(spt, 2, "Access violation", tp);
       return;
   }

   /* check if the file exists */
   if (tftp_read_data(spt, 0, NULL, 0) < 0) {
       tftp_send_error(spt, 1, "File not found", tp);
       return;
   }

   if (tp->x.tp_buf[pktlen - 1] != 0) {
       tftp_send_error(spt, 2, "Access violation", tp);
       return;
   }

   while (k < pktlen && nb_options < ARRAY_SIZE(option_name)) {
       const char *key, *value;

       key = &tp->x.tp_buf[k];
       k += strlen(key) + 1;

       if (k >= pktlen) {
           tftp_send_error(spt, 2, "Access violation", tp);
           return;
       }

       value = &tp->x.tp_buf[k];
       k += strlen(value) + 1;

       if (strcasecmp(key, "tsize") == 0) {
           int tsize = atoi(value);
           struct stat stat_p;

           if (tsize == 0) {
               if (stat(spt->filename, &stat_p) == 0)
                   tsize = stat_p.st_size;
               else {
                   tftp_send_error(spt, 1, "File not found", tp);
                   return;
               }
           }

           option_name[nb_options] = "tsize";
           option_value[nb_options] = tsize;
           nb_options++;
       } else if (strcasecmp(key, "blksize") == 0) {
           int blksize = atoi(value);

           /* If blksize option is bigger than what we will
            * emit, accept the option with our packet size.
            * Otherwise, simply do as we didn't see the option.
            */
           if (blksize >= 512) {
               option_name[nb_options] = "blksize";
               option_value[nb_options] = 512;
               nb_options++;
           }
       }
   }

   if (nb_options > 0) {
       assert(nb_options <= ARRAY_SIZE(option_name));
       tftp_send_oack(spt, option_name, option_value, nb_options, tp);
       return;
   }

   spt->block_nr = 0;
   tftp_send_next_block(spt, tp);
 }

 static void tftp_handle_ack(Slirp *slirp, struct tftp_t *tp, int pktlen)
 {
   int s;

   s = tftp_session_find(slirp, tp);

   if (s < 0) {
     return;
   }

   tftp_send_next_block(&slirp->tftp_sessions[s], tp);
 }

 static void tftp_handle_error(Slirp *slirp, struct tftp_t *tp, int pktlen)
 {
   int s;

   s = tftp_session_find(slirp, tp);

   if (s < 0) {
     return;
   }

   tftp_session_terminate(&slirp->tftp_sessions[s]);
 }

 void tftp_input(struct mbuf *m)
 {
   struct tftp_t *tp = (struct tftp_t *)m->m_data;

   switch(ntohs(tp->tp_op)) {
   case TFTP_RRQ:
     tftp_handle_rrq(m->slirp, tp, m->m_len);
     break;

   case TFTP_ACK:
     tftp_handle_ack(m->slirp, tp, m->m_len);
     break;

   case TFTP_ERROR:
     tftp_handle_error(m->slirp, tp, m->m_len);
     break;
   }
 }
	/*
	* tftp.c - a simple, read-only tftp server for qemu
	*
	* Copyright (c) 2004 Magnus Damm <damm@opensource.se>
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	#include <slirp.h>
	#include "qemu-common.h"

	static inline int tftp_session_in_use(struct tftp_session *spt)
	{
	return (spt->slirp != NULL);
	}

	static inline void tftp_session_update(struct tftp_session *spt)
	{
	spt->timestamp = curtime;
	}

	static void tftp_session_terminate(struct tftp_session *spt)
	{
	if (spt->f != NULL) {
	fclose(spt->f);
	spt->f = NULL;
	}
	g_free(spt->filename);
	spt->slirp = NULL;
	}

	static int tftp_session_allocate(Slirp slirp, struct tftp_t tp)
	{
	struct tftp_session *spt;
	int k;

	for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
	spt = &slirp->tftp_sessions[k];

	if (!tftp_session_in_use(spt))
	goto found;

	/* sessions time out after 5 inactive seconds */
	if ((int)(curtime - spt->timestamp) > 5000) {
	tftp_session_terminate(spt);
	goto found;
	}
	}

	return -1;

	found:
	memset(spt, 0, sizeof(*spt));
	memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
	spt->f = NULL;
	spt->client_port = tp->udp.uh_sport;
	spt->slirp = slirp;

	tftp_session_update(spt);

	return k;
	}

	static int tftp_session_find(Slirp slirp, struct tftp_t tp)
	{
	struct tftp_session *spt;
	int k;

	for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
	spt = &slirp->tftp_sessions[k];

	if (tftp_session_in_use(spt)) {
	if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
	if (spt->client_port == tp->udp.uh_sport) {
	return k;
	}
	}
	}
	}

	return -1;
	}

	static int tftp_read_data(struct tftp_session *spt, uint32_t block_nr,
	uint8_t *buf, int len)
	{
	int bytes_read = 0;

	if (spt->f == NULL) {
	spt->f = fopen(spt->filename, "rb");
	}

	if (spt->f == NULL) {
	return -1;
	}

	if (len) {
	fseek(spt->f, block_nr * 512, SEEK_SET);

	bytes_read = fread(buf, 1, len, spt->f);
	}

	return bytes_read;
	}

	static int tftp_send_oack(struct tftp_session *spt,
	const char *keys[], uint32_t values[], int nb,
	struct tftp_t *recv_tp)
	{
	struct sockaddr_in saddr, daddr;
	struct mbuf *m;
	struct tftp_t *tp;
	int i, n = 0;

	m = m_get(spt->slirp);

	if (!m)
	return -1;

	memset(m->m_data, 0, m->m_size);

	m->m_data += IF_MAXLINKHDR;
	tp = (struct tftp_t *)m->m_data;
	m->m_data += sizeof(struct udpiphdr);

	tp->tp_op = htons(TFTP_OACK);
	for (i = 0; i < nb; i++) {
	n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
	keys[i]) + 1;
	n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
	values[i]) + 1;
	}

	saddr.sin_addr = recv_tp->ip.ip_dst;
	saddr.sin_port = recv_tp->udp.uh_dport;

	daddr.sin_addr = spt->client_ip;
	daddr.sin_port = spt->client_port;

	m->m_len = sizeof(struct tftp_t) - 514 + n -
	sizeof(struct ip) - sizeof(struct udphdr);
	udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

	return 0;
	}

	static void tftp_send_error(struct tftp_session *spt,
	uint16_t errorcode, const char *msg,
	struct tftp_t *recv_tp)
	{
	struct sockaddr_in saddr, daddr;
	struct mbuf *m;
	struct tftp_t *tp;

	m = m_get(spt->slirp);

	if (!m) {
	goto out;
	}

	memset(m->m_data, 0, m->m_size);

	m->m_data += IF_MAXLINKHDR;
	tp = (struct tftp_t *)m->m_data;
	m->m_data += sizeof(struct udpiphdr);

	tp->tp_op = htons(TFTP_ERROR);
	tp->x.tp_error.tp_error_code = htons(errorcode);
	pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);

	saddr.sin_addr = recv_tp->ip.ip_dst;
	saddr.sin_port = recv_tp->udp.uh_dport;

	daddr.sin_addr = spt->client_ip;
	daddr.sin_port = spt->client_port;

	m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
	sizeof(struct ip) - sizeof(struct udphdr);

	udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

	out:
	tftp_session_terminate(spt);
	}

	static void tftp_send_next_block(struct tftp_session *spt,
	struct tftp_t *recv_tp)
	{
	struct sockaddr_in saddr, daddr;
	struct mbuf *m;
	struct tftp_t *tp;
	int nobytes;

	m = m_get(spt->slirp);

	if (!m) {
	return;
	}

	memset(m->m_data, 0, m->m_size);

	m->m_data += IF_MAXLINKHDR;
	tp = (struct tftp_t *)m->m_data;
	m->m_data += sizeof(struct udpiphdr);

	tp->tp_op = htons(TFTP_DATA);
	tp->x.tp_data.tp_block_nr = htons((spt->block_nr + 1) & 0xffff);

	saddr.sin_addr = recv_tp->ip.ip_dst;
	saddr.sin_port = recv_tp->udp.uh_dport;

	daddr.sin_addr = spt->client_ip;
	daddr.sin_port = spt->client_port;

	nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf, 512);

	if (nobytes < 0) {
	m_free(m);

	/* send "file not found" error back */

	tftp_send_error(spt, 1, "File not found", tp);

	return;
	}

	m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
	sizeof(struct ip) - sizeof(struct udphdr);

	udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

	if (nobytes == 512) {
	tftp_session_update(spt);
	}
	else {
	tftp_session_terminate(spt);
	}

	spt->block_nr++;
	}

	static void tftp_handle_rrq(Slirp slirp, struct tftp_t tp, int pktlen)
	{
	struct tftp_session *spt;
	int s, k;
	size_t prefix_len;
	char *req_fname;
	const char *option_name[2];
	uint32_t option_value[2];
	int nb_options = 0;

	/* check if a session already exists and if so terminate it */
	s = tftp_session_find(slirp, tp);
	if (s >= 0) {
	tftp_session_terminate(&slirp->tftp_sessions[s]);
	}

	s = tftp_session_allocate(slirp, tp);

	if (s < 0) {
	return;
	}

	spt = &slirp->tftp_sessions[s];

	/* unspecified prefix means service disabled */
	if (!slirp->tftp_prefix) {
	tftp_send_error(spt, 2, "Access violation", tp);
	return;
	}

	/* skip header fields */
	k = 0;
	pktlen -= offsetof(struct tftp_t, x.tp_buf);

	/* prepend tftp_prefix */
	prefix_len = strlen(slirp->tftp_prefix);
	spt->filename = (char *)g_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
	memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
	spt->filename[prefix_len] = '/';

	/* get name */
	req_fname = spt->filename + prefix_len + 1;

	while (1) {
	if (k >= TFTP_FILENAME_MAX \|\| k >= pktlen) {
	tftp_send_error(spt, 2, "Access violation", tp);
	return;
	}
	req_fname[k] = tp->x.tp_buf[k];
	if (req_fname[k++] == '\0') {
	break;
	}
	}

	/* check mode */
	if ((pktlen - k) < 6) {
	tftp_send_error(spt, 2, "Access violation", tp);
	return;
	}

	if (strcasecmp(&tp->x.tp_buf[k], "octet") != 0) {
	tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
	return;
	}

	k += 6; /* skipping octet */

	/* do sanity checks on the filename */
	if (!strncmp(req_fname, "../", 3) \|\|
	req_fname[strlen(req_fname) - 1] == '/' \|\|
	strstr(req_fname, "/../")) {
	tftp_send_error(spt, 2, "Access violation", tp);
	return;
	}

	/* check if the file exists */
	if (tftp_read_data(spt, 0, NULL, 0) < 0) {
	tftp_send_error(spt, 1, "File not found", tp);
	return;
	}

	if (tp->x.tp_buf[pktlen - 1] != 0) {
	tftp_send_error(spt, 2, "Access violation", tp);
	return;
	}

	while (k < pktlen && nb_options < ARRAY_SIZE(option_name)) {
	const char key, value;

	key = &tp->x.tp_buf[k];
	k += strlen(key) + 1;

	if (k >= pktlen) {
	tftp_send_error(spt, 2, "Access violation", tp);
	return;
	}

	value = &tp->x.tp_buf[k];
	k += strlen(value) + 1;

	if (strcasecmp(key, "tsize") == 0) {
	int tsize = atoi(value);
	struct stat stat_p;

	if (tsize == 0) {
	if (stat(spt->filename, &stat_p) == 0)
	tsize = stat_p.st_size;
	else {
	tftp_send_error(spt, 1, "File not found", tp);
	return;
	}
	}

	option_name[nb_options] = "tsize";
	option_value[nb_options] = tsize;
	nb_options++;
	} else if (strcasecmp(key, "blksize") == 0) {
	int blksize = atoi(value);

	/* If blksize option is bigger than what we will
	* emit, accept the option with our packet size.
	* Otherwise, simply do as we didn't see the option.
	*/
	if (blksize >= 512) {
	option_name[nb_options] = "blksize";
	option_value[nb_options] = 512;
	nb_options++;
	}
	}
	}

	if (nb_options > 0) {
	assert(nb_options <= ARRAY_SIZE(option_name));
	tftp_send_oack(spt, option_name, option_value, nb_options, tp);
	return;
	}

	spt->block_nr = 0;
	tftp_send_next_block(spt, tp);
	}

	static void tftp_handle_ack(Slirp slirp, struct tftp_t tp, int pktlen)
	{
	int s;

	s = tftp_session_find(slirp, tp);

	if (s < 0) {
	return;
	}

	tftp_send_next_block(&slirp->tftp_sessions[s], tp);
	}

	static void tftp_handle_error(Slirp slirp, struct tftp_t tp, int pktlen)
	{
	int s;

	s = tftp_session_find(slirp, tp);

	if (s < 0) {
	return;
	}

	tftp_session_terminate(&slirp->tftp_sessions[s]);
	}

	void tftp_input(struct mbuf *m)
	{
	struct tftp_t tp = (struct tftp_t )m->m_data;

	switch(ntohs(tp->tp_op)) {
	case TFTP_RRQ:
	tftp_handle_rrq(m->slirp, tp, m->m_len);
	break;

	case TFTP_ACK:
	tftp_handle_ack(m->slirp, tp, m->m_len);
	break;

	case TFTP_ERROR:
	tftp_handle_error(m->slirp, tp, m->m_len);
	break;
	}
	}