Hello everyone,
I think there is a small bug in RIOT/pkg/lwip/contrib/sock/tcp/lwip_sock_tcp.c
346 /* post-process buf */
347 if (buf_len > copylen) {
348 /* there is still data in the buffer */
349 sock->last_buf = buf;
350 sock->last_offset = copylen;
351 }
In line 350, I guess it should be sock->last_offset += copylen;\
The problem occurs when I read a message from the socket buffer by multiple (more than two) calls to
sock_tcp_read(...).
Example:
There is a buffer of 10 Bytes available and in the first call I read 8 Bytes.
We’ll have sock->last_buf set and sock->last_offset is 8.\
In the next step we read 1 Byte (copylen = 1).
The remaining buffer length is computed by
337 buf_len = buf->tot_len - sock->last_offset;
and obviously is 2.
There is still data in the buffer left to read, so again we’ll have sock->last_buf set and sock->last_offset now is 1, since copylen = 1.
If we want to read the last remaining Byte, we’ll compute the remaining buffer length to
buf_len = buf->tot_len - sock->last_offset
10 - 1 = 9
which should not be the case.
The problem occurs when I want to read new data from the socket buffer.
Then I get the pointer of the old buffer with a wrong sock->last_offset value and with the previous example I would start reading at offset 1.
sock->last_offset += copylen; should solve the issue, since it properly increments the last offset and the remaining buffer length will be computed correctly.
Regards