issue 469: Implement Packet Loss Simulation for TQUIC Tools

[Chi-Kai]

This PR implements comprehensive packet loss simulation capabilities for TQUIC tools, enabling testing of network resilience and protocol behavior under adverse conditions.

closed #469

Features Implemented

Packet Header Parsing

• Added packet header parsing interface to extract packet sequence numbers and types
• Utilizes PacketHeader::from_bytes() for robust packet analysis
• Supports all QUIC packet types: Initial, ZeroRTT, Handshake, OneRTT, Retry, VersionNegotiation

Packet Loss Simulation

• Random Loss: Configurable loss rate (0.0 to 1.0) with uniform distribution
• Specific Packet Numbers: Target exact packet sequence numbers for testing
• Packet Type Filtering: Drop specific packet types (e.g., handshake packets only)
• Directional Control: Separate control for incoming vs outgoing packet loss

Command Line Interface

Added new parameters to both tquic_client and tquic_server:

  --packet-loss-rate <RATE>         # Random loss rate (0.0-1.0)
  --packet-loss-numbers <NUMBERS>   # Comma-separated packet numbers
  --packet-loss-types <TYPES>       # Packet types to drop
  --packet-loss-incoming            # Apply to incoming packets  
  --packet-loss-outgoing            # Apply to outgoing packets

Implementation Details

Core Components:

• tools/src/packet_loss.rs: Main simulation logic and configuration
• tools/src/common.rs: Integration with QuicSocket for packet interception
• Updated client/server binaries with CLI parameter support

Integration Points:

• Receive Path: Intercepts packets in recv_from() before processing
• Send Path: Intercepts packets in send_to() before transmission
• Error Handling: Uses WouldBlock to simulate dropped packets gracefully

Usage Examples

# Server with 10% random packet loss
./tquic_server --packet-loss-rate 0.1 --packet-loss-outgoing

# Client dropping handshake packets
./tquic_client --packet-loss-types handshake --packet-loss-outgoing --connect-to 127.0.0.1:8443 https://example.org

# Combined testing with specific packet numbers
./tquic_client --packet-loss-numbers 1,5,10 --packet-loss-incoming --connect-to 127.0.0.1:8443 https://example.org

Test

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.72%. Comparing base (b62863a) to head (7325353).

Additional details and impacted files

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##           develop     #477   +/-   ##
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  Coverage    94.72%   94.72%           
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  Files           50       50           
  Lines        30282    30282           
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  Hits         28685    28685           
  Misses        1597     1597           

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