Module tcp_sack 

TCP Selective Acknowledgment (SACK) implementation

Implements RFC 2018 TCP SACK option parsing, scoreboard tracking, and selective retransmission hole detection. Enables efficient recovery from multiple segment losses without retransmitting already-received data.

Structs

SackBlock

A single SACK block representing a contiguous range of received bytes.

SackScoreboard

Tracks selectively acknowledged ranges for a TCP connection.

Constants

MAX_SACK_BLOCKS

Maximum number of SACK blocks in a single TCP option (limited by option space)

TCP_OPT_SACK

TCP option kind for SACK blocks

TCP_OPT_SACK_PERMITTED

TCP option kind for SACK-Permitted (sent in SYN/SYN-ACK)

TCP_OPT_SACK_PERMITTED_LEN

TCP option length for SACK-Permitted

Functions

has_sack_permitted

Check if SACK-Permitted option is present in TCP options.

parse_sack_blocks

Parse SACK blocks from TCP options bytes.

seq_ge

Returns true if a >= b in sequence space.

seq_gt

Returns true if a > b in sequence space.

seq_le

Returns true if a <= b in sequence space.

seq_lt

Compare sequence numbers using signed 32-bit difference. Returns true if a is strictly less than b in sequence space.

serialize_sack_blocks

Serialize SACK blocks into TCP option bytes.

serialize_sack_permitted

Serialize SACK-Permitted option (2 bytes, for SYN/SYN-ACK).