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Fix sequence number addition/subtraction when wrapping around

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Fixes #115
This commit is contained in:
Matias Fontanini
2016-01-10 16:31:48 -08:00
parent 2169b1f71f
commit b21154a926
1 changed files with 3 additions and 12 deletions
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15
src/tcp_stream.cpp
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@@ -38,24 +38,15 @@ namespace Tins {
// As defined by RFC 1982 - 2 ^ (SERIAL_BITS - 1) // As defined by RFC 1982 - 2 ^ (SERIAL_BITS - 1)
static const uint32_t seq_number_diff = 2147483648U; static const uint32_t seq_number_diff = 2147483648U;
// As defined by RFC 1982 - 2 ^ (SERIAL_BITS)
static const uint32_t addition_modulo = numeric_limits<uint32_t>::max();
// Sequence number add as defined by RFC 1982 // Adds sequence numbers
uint32_t add_sequence_numbers(uint32_t seq1, uint32_t seq2) { uint32_t add_sequence_numbers(uint32_t seq1, uint32_t seq2) {
return (static_cast<uint64_t>(seq1) + seq2) % addition_modulo; return seq1 + seq2;
} }
// Subtract sequence numbers // Subtract sequence numbers
uint32_t subtract_sequence_numbers(uint32_t seq1, uint32_t seq2) { uint32_t subtract_sequence_numbers(uint32_t seq1, uint32_t seq2) {
if (seq1 > seq2) { return seq1 - seq2;
return seq1 - seq2;
}
else {
// the numbers between seq2 and the maximum sequence number(including seq1)
// + the numbers between 0 and seq1
return (numeric_limits<uint32_t>::max() - seq2) + seq1 + 1;
}
} }
// Compares sequence numbers as defined by RFC 1982. // Compares sequence numbers as defined by RFC 1982.