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examples/client: Fix Block1 handling for growing block sizes

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Only increment block size if it can be done without causing gaps or
overlaps in the byte sequence.

The patch adds a check for alignment to ensure that no gaps appear when
a server responds with a larger block size than the original request
was using.

Ignore the block number sent by the server since that may or may not be
valid. Always recompute based on how many bytes have been sent so far.

Rationale:

Erbium (Contiki CoAP) responds to Block1 request with a Block1 option
containing the server's maximum supported Block1 size (Contiki
configuration option REST_MAX_CHUNK_SIZE). However, the block number
in the Block1 option is the same number as the block number of the
original request.
This commit is contained in:
Joakim Nohlgård committed 2016-12-02 09:52:17 +01:00
1 parent 72eec07777
commit f7a17c975e
1 file changed
+18 -5
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examples/client.c
+18 -5
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@@ -426,11 +426,24 @@ message_handler(struct coap_context_t *ctx,
block_opt = coap_check_option(received, COAP_OPTION_BLOCK1, &opt_iter);
if (block_opt) { /* handle Block1 */
block.szx = COAP_OPT_BLOCK_SZX(block_opt);
block.num = coap_opt_block_num(block_opt);
debug("found Block1, block size is %u, block nr. %u\n",
block.szx, block.num);
unsigned int szx = COAP_OPT_BLOCK_SZX(block_opt);
unsigned int num = coap_opt_block_num(block_opt);
debug("found Block1 option, block size is %u, block nr. %u\n", szx, num);
if (szx != block.szx) {
unsigned int bytes_sent = ((block.num + 1) << (block.szx + 4));
if (bytes_sent % (1 << (szx + 4)) == 0) {
/* Recompute the block number of the previous packet given the new block size */
block.num = (bytes_sent >> (szx + 4)) - 1;
block.szx = szx;
debug("new Block1 size is %u, block number %u completed\n", (1 << (block.szx + 4)), block.num);
} else {
debug("ignoring request to increase Block1 size, "
"next block is not aligned on requested block size boundary. "
"(%u x %u mod %u = %u != 0)\n",
block.num + 1, (1 << (block.szx + 4)), (1 << (szx + 4)),
bytes_sent % (1 << (szx + 4)));
}
}
if (payload.length <= (block.num+1) * (1 << (block.szx + 4))) {
debug("upload ready\n");