Fix bug with packet sizes - #559
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This is an import of OpenKermit/ckermit@d560c58 Original description: The initial bug can be duplicated with this command, which will hang: touch /tmp/foobar12345 kermit -H -Y -C "set host /network-type:pseudoterminal kermit -x, remote del /tmp/foobar12345, close, exit" Note that the /tmp/foobar12345 filename is the precise length needed to trigger this. When long packets are negotiated, kermit switches to long packet formatting (extended length) if the total packet size (excluding SOP and the LEN byte itself) exceeds the maximum length that can be represented as a single printable ASCII character in the short packet's LEN field. Since short packet lengths are encoded via tochar(len) = len + 32, and the maximum printable ASCII character is '~' (126), the maximum value that can be encoded in the short LEN field is 126 - 32 = 94 bytes. Any packet where (len + bctl + 2) exceeds 94 must be formatted as a long packet. The previous threshold of > 96 was incorrect and caused packets of size 95 and 96 to be formatted as short packets. This resulted packes of size 95 or 96 generating a len byte of 127 (0x7f) or 128 (0x80), which the receiving end rejected.
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This is an import of
OpenKermit/ckermit@d560c58
Original description:
The initial bug can be duplicated with this command, which will hang:
Note that the /tmp/foobar12345 filename is the precise length needed to trigger this.
When long packets are negotiated, kermit switches to long packet formatting (extended length) if the total packet size (excluding SOP and the LEN byte itself) exceeds the maximum length that can be represented as a single printable ASCII character in the short packet's LEN field.
Since short packet lengths are encoded via tochar(len) = len + 32, and the maximum printable ASCII character is '~' (126), the maximum value that can be encoded in the short LEN field is 126 - 32 = 94 bytes.
Any packet where (len + bctl + 2) exceeds 94 must be formatted as a long packet. The previous threshold of > 96 was incorrect and caused packets of size 95 and 96 to be formatted as short packets.
This resulted packes of size 95 or 96 generating a len byte of 127 (0x7f) or 128 (0x80), which the receiving end rejected.