slirp: support dynamic block size for TFTP transfers

The blocksize option is defined in RFC 1783 and RFC 2348.
We now support block sizes between 1 and 1428 bytes, instead of 512 only.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

2 files changed, 20 insertions, 16 deletions

diff --git a/tftp.c b/tftp.c
index 4f76743..fdb8cb2 100644
--- a/tftp.c
+++ b/tftp.c
@@ -72,6 +72,7 @@ found:
     memset(spt, 0, sizeof(*spt));
     spt->client_addr = *srcsas;
     spt->fd = -1;
+    spt->block_size = 512;
     spt->client_port = tp->udp.uh_sport;
     spt->slirp = slirp;
 
@@ -115,7 +116,7 @@ static int tftp_read_data(struct tftp_session *spt, uint32_t block_nr,
     }
 
     if (len) {
-        lseek(spt->fd, block_nr * 512, SEEK_SET);
+        lseek(spt->fd, block_nr * spt->block_size, SEEK_SET);
 
         bytes_read = read(spt->fd, buf, len);
     }
@@ -190,7 +191,8 @@ static int tftp_send_oack(struct tftp_session *spt, const char *keys[],
              1;
     }
 
-    m->m_len = sizeof(struct tftp_t) - 514 + n - sizeof(struct udphdr);
+    m->m_len = sizeof(struct tftp_t) - (TFTP_BLOCKSIZE_MAX + 2) + n -
+               sizeof(struct udphdr);
     tftp_udp_output(spt, m, recv_tp);
 
     return 0;
@@ -214,8 +216,8 @@ static void tftp_send_error(struct tftp_session *spt, uint16_t errorcode,
     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);
 
-    m->m_len =
-        sizeof(struct tftp_t) - 514 + 3 + strlen(msg) - sizeof(struct udphdr);
+    m->m_len = sizeof(struct tftp_t) - (TFTP_BLOCKSIZE_MAX + 2) + 3 +
+               strlen(msg) - sizeof(struct udphdr);
     tftp_udp_output(spt, m, recv_tp);
 
 out:
@@ -240,7 +242,8 @@ static void tftp_send_next_block(struct tftp_session *spt,
     tp->tp_op = htons(TFTP_DATA);
     tp->x.tp_data.tp_block_nr = htons((spt->block_nr + 1) & 0xffff);
 
-    nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf, 512);
+    nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf,
+                             spt->block_size);
 
     if (nobytes < 0) {
         m_free(m);
@@ -252,10 +255,11 @@ static void tftp_send_next_block(struct tftp_session *spt,
         return;
     }
 
-    m->m_len = sizeof(struct tftp_t) - (512 - nobytes) - sizeof(struct udphdr);
+    m->m_len = sizeof(struct tftp_t) - (TFTP_BLOCKSIZE_MAX - nobytes) -
+               sizeof(struct udphdr);
     tftp_udp_output(spt, m, recv_tp);
 
-    if (nobytes == 512) {
+    if (nobytes == spt->block_size) {
         tftp_session_update(spt);
     } else {
         tftp_session_terminate(spt);
@@ -383,13 +387,11 @@ static void tftp_handle_rrq(Slirp *slirp, struct sockaddr_storage *srcsas,
         } 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) {
+            /* Accept blksize up to our maximum size */
+            if (blksize > 0) {
+                spt->block_size = MIN(blksize, TFTP_BLOCKSIZE_MAX);
                 option_name[nb_options] = "blksize";
-                option_value[nb_options] = 512;
+                option_value[nb_options] = spt->block_size;
                 nb_options++;
             }
         }
diff --git a/tftp.h b/tftp.h
index 9d8cecb..dcb1048 100644
--- a/tftp.h
+++ b/tftp.h
@@ -15,6 +15,7 @@
 #define TFTP_OACK 6
 
 #define TFTP_FILENAME_MAX 512
+#define TFTP_BLOCKSIZE_MAX 1428
 
 struct tftp_t {
     struct udphdr udp;
@@ -22,13 +23,13 @@ struct tftp_t {
     union {
         struct {
             uint16_t tp_block_nr;
-            uint8_t tp_buf[512];
+            uint8_t tp_buf[TFTP_BLOCKSIZE_MAX];
         } tp_data;
         struct {
             uint16_t tp_error_code;
-            uint8_t tp_msg[512];
+            uint8_t tp_msg[TFTP_BLOCKSIZE_MAX];
         } tp_error;
-        char tp_buf[512 + 2];
+        char tp_buf[TFTP_BLOCKSIZE_MAX + 2];
     } x;
 } __attribute__((packed));
 
@@ -36,6 +37,7 @@ struct tftp_session {
     Slirp *slirp;
     char *filename;
     int fd;
+    uint16_t block_size;
 
     struct sockaddr_storage client_addr;
     uint16_t client_port;