Greptile Summary

This PR adds a Teredo embedding strategy (src/Strategy/Teredo.php) that extracts and packs IPv4 addresses according to RFC 4380 § 4, matching the 2001:0000::/32 prefix and XOR-obfuscating the client IPv4 in the last 32 bits. It follows the established pattern of the existing Mapped, Derived, and Nat64 strategies.

• Strategy implementation (src/Strategy/Teredo.php): isEmbedded checks the 32-bit Teredo prefix, extract XORs bytes 12–15 with 0xFFFFFFFF per the RFC, and pack constructs the canonical Teredo form (zero server/flags/port). The documented asymmetry between extraction and packing for non-canonical addresses is intentional and matches the Derived strategy's behaviour.
• Test data (tests/DataProvider/Strategy/Teredo.php): Vectors are verified against the RFC 4380 worked example (server 65.54.227.120, client 192.0.2.45) and cover canonical, non-canonical, and loopback-embedding cases.
• IpDataProviderInterface bit-flag renumbering: TEREDO = 1 << 26 is inserted between COMPATIBLE and the existing LOOPBACK_* group, shifting LOOPBACK_MAPPED/COMPATIBLE/DERIVED each up by one bit. These are test-internal constants referenced only by name, so the shift is safe.

Confidence Score: 5/5

The change is self-contained and additive — new strategy class, new test data provider, and one new test method; no existing production paths are modified.

The Teredo prefix check, XOR extraction, and canonical packing all match RFC 4380 § 4 and are verified against the RFC's own worked example. The bit-flag renumbering in the test interface is safe because every usage references the constants by name. The related ip-doctrine library makes no reference to embedding strategies and is unaffected.

No files require special attention.

Important Files Changed

Sequence Diagram

sequenceDiagram
    participant Caller
    participant Teredo as Strategy\Teredo
    participant Binary as Util\Binary
    participant MbString as Util\MbString

    note over Caller,MbString: isEmbedded - prefix detection
    Caller->>Teredo: isEmbedded(binary)
    Teredo->>MbString: "getLength(binary) == 16?"
    Teredo->>MbString: subString(binary, 0, 4)
    Teredo->>Binary: fromHex('20010000')
    Teredo-->>Caller: "true if first 4 bytes == 2001:0000"

    note over Caller,MbString: extract - client IPv4 recovery
    Caller->>Teredo: extract(binary)
    Teredo->>MbString: "getLength(binary) == 16?"
    Teredo->>MbString: subString(binary, 12, 4)
    note right of Teredo: XOR last 4 bytes with 0xFFFFFFFF
    Teredo-->>Caller: 4-byte client IPv4

    note over Caller,MbString: pack - canonical Teredo construction
    Caller->>Teredo: pack(ipv4binary)
    Teredo->>MbString: "getLength(ipv4binary) == 4?"
    Teredo->>Binary: fromHex('20010000') prefix
    Teredo->>Binary: fromHex('0000000000000000') zeroed fields
    note right of Teredo: XOR IPv4 with 0xFFFFFFFF
    Teredo-->>Caller: 16-byte canonical Teredo address

_{Reviews (2): Last reviewed commit: "feature(strategy): ✨ add Teredo (RFC4380..." | Re-trigger Greptile}