diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index 025b3743678b80fe72891e01ca8f0d61551cf7e4..1542e4361920ec1773c966cadf4f193ea3578783 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -114,9 +114,9 @@ tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
 	int win = 0;
 
 	DEBUG_CALL("tcp_respond");
-	DEBUG_ARG("tp = %lx", (long)tp);
-	DEBUG_ARG("ti = %lx", (long)ti);
-	DEBUG_ARG("m = %lx", (long)m);
+	DEBUG_ARG("tp = %p", tp);
+	DEBUG_ARG("ti = %p", ti);
+	DEBUG_ARG("m = %p", m);
 	DEBUG_ARG("ack = %u", ack);
 	DEBUG_ARG("seq = %u", seq);
 	DEBUG_ARG("flags = %x", flags);
@@ -124,7 +124,7 @@ tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
 	if (tp)
 		win = sbspace(&tp->t_socket->so_rcv);
         if (m == NULL) {
-		if ((m = m_get(tp->t_socket->slirp)) == NULL)
+		if (!tp || (m = m_get(tp->t_socket->slirp)) == NULL)
 			return;
 		tlen = 0;
 		m->m_data += IF_MAXLINKHDR;
diff --git a/slirp/tftp.c b/slirp/tftp.c
index b78765f3af1b0febd7feea6a98f422b6b9207b81..1a79c45cfb6034e1746f2f0e2f48f10f65e60203 100644
--- a/slirp/tftp.c
+++ b/slirp/tftp.c
@@ -37,6 +37,10 @@ static inline void tftp_session_update(struct tftp_session *spt)
 
 static void tftp_session_terminate(struct tftp_session *spt)
 {
+    if (spt->fd >= 0) {
+        close(spt->fd);
+        spt->fd = -1;
+    }
     g_free(spt->filename);
     spt->slirp = NULL;
 }
@@ -54,7 +58,7 @@ static int tftp_session_allocate(Slirp *slirp, struct tftp_t *tp)
 
     /* sessions time out after 5 inactive seconds */
     if ((int)(curtime - spt->timestamp) > 5000) {
-        g_free(spt->filename);
+        tftp_session_terminate(spt);
         goto found;
     }
   }
@@ -64,6 +68,7 @@ static int tftp_session_allocate(Slirp *slirp, struct tftp_t *tp)
  found:
   memset(spt, 0, sizeof(*spt));
   memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
+  spt->fd = -1;
   spt->client_port = tp->udp.uh_sport;
   spt->slirp = slirp;
 
@@ -92,37 +97,36 @@ static int tftp_session_find(Slirp *slirp, struct tftp_t *tp)
   return -1;
 }
 
-static int tftp_read_data(struct tftp_session *spt, uint16_t block_nr,
+static int tftp_read_data(struct tftp_session *spt, uint32_t block_nr,
                           uint8_t *buf, int len)
 {
-  int fd;
-  int bytes_read = 0;
+    int bytes_read = 0;
 
-  fd = open(spt->filename, O_RDONLY | O_BINARY);
+    if (spt->fd < 0) {
+        spt->fd = open(spt->filename, O_RDONLY | O_BINARY);
+    }
 
-  if (fd < 0) {
-    return -1;
-  }
+    if (spt->fd < 0) {
+        return -1;
+    }
 
-  if (len) {
-    lseek(fd, block_nr * 512, SEEK_SET);
+    if (len) {
+        lseek(spt->fd, block_nr * 512, SEEK_SET);
 
-    bytes_read = read(fd, buf, len);
-  }
-
-  close(fd);
+        bytes_read = read(spt->fd, buf, len);
+    }
 
-  return bytes_read;
+    return bytes_read;
 }
 
 static int tftp_send_oack(struct tftp_session *spt,
-                          const char *key, uint32_t value,
+                          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 n = 0;
+    int i, n = 0;
 
     m = m_get(spt->slirp);
 
@@ -136,10 +140,12 @@ static int tftp_send_oack(struct tftp_session *spt,
     m->m_data += sizeof(struct udpiphdr);
 
     tp->tp_op = htons(TFTP_OACK);
-    n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
-                  key) + 1;
-    n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
-                  value) + 1;
+    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;
@@ -193,23 +199,18 @@ out:
   tftp_session_terminate(spt);
 }
 
-static int tftp_send_data(struct tftp_session *spt,
-                          uint16_t block_nr,
-			  struct tftp_t *recv_tp)
+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;
 
-  if (block_nr < 1) {
-    return -1;
-  }
-
   m = m_get(spt->slirp);
 
   if (!m) {
-    return -1;
+    return;
   }
 
   memset(m->m_data, 0, m->m_size);
@@ -219,7 +220,7 @@ static int tftp_send_data(struct tftp_session *spt,
   m->m_data += sizeof(struct udpiphdr);
 
   tp->tp_op = htons(TFTP_DATA);
-  tp->x.tp_data.tp_block_nr = htons(block_nr);
+  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;
@@ -227,7 +228,7 @@ static int tftp_send_data(struct tftp_session *spt,
   daddr.sin_addr = spt->client_ip;
   daddr.sin_port = spt->client_port;
 
-  nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
+  nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf, 512);
 
   if (nobytes < 0) {
     m_free(m);
@@ -236,7 +237,7 @@ static int tftp_send_data(struct tftp_session *spt,
 
     tftp_send_error(spt, 1, "File not found", tp);
 
-    return -1;
+    return;
   }
 
   m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
@@ -251,7 +252,7 @@ static int tftp_send_data(struct tftp_session *spt,
     tftp_session_terminate(spt);
   }
 
-  return 0;
+  spt->block_nr++;
 }
 
 static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
@@ -260,6 +261,9 @@ static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
   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);
@@ -337,7 +341,7 @@ static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
       return;
   }
 
-  while (k < pktlen) {
+  while (k < pktlen && nb_options < ARRAY_SIZE(option_name)) {
       const char *key, *value;
 
       key = &tp->x.tp_buf[k];
@@ -364,12 +368,32 @@ static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
 	      }
 	  }
 
-	  tftp_send_oack(spt, "tsize", tsize, 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++;
+          }
       }
   }
 
-  tftp_send_data(spt, 1, tp);
+  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)
@@ -382,11 +406,7 @@ static void tftp_handle_ack(Slirp *slirp, struct tftp_t *tp, int pktlen)
     return;
   }
 
-  if (tftp_send_data(&slirp->tftp_sessions[s],
-		     ntohs(tp->x.tp_data.tp_block_nr) + 1,
-		     tp) < 0) {
-    return;
-  }
+  tftp_send_next_block(&slirp->tftp_sessions[s], tp);
 }
 
 static void tftp_handle_error(Slirp *slirp, struct tftp_t *tp, int pktlen)
diff --git a/slirp/tftp.h b/slirp/tftp.h
index 72e5e91bef6bccc35d7788d40bd29c8686569638..51704e48747caa3b2007c955a0c7bf8659bb96b8 100644
--- a/slirp/tftp.h
+++ b/slirp/tftp.h
@@ -33,9 +33,11 @@ struct tftp_t {
 struct tftp_session {
     Slirp *slirp;
     char *filename;
+    int fd;
 
     struct in_addr client_ip;
     uint16_t client_port;
+    uint32_t block_nr;
 
     int timestamp;
 };