[Fix] IP Address Conversion Functions for Proper IPv4-Mapped IPv6 Format (Issue #641) by s-cu-bot · Pull Request #690 · projectdiscovery/mapcidr

s-cu-bot · 2025-09-20T08:12:38Z

Fix IPv6 → IPv4 Conversion and Adjust IPv4-to-IPv6 Mapping Format

Summary

This PR fixes the IPv6 ↔ IPv4 conversion logic in mapcidr with two key changes:

IPv6 → IPv4 conversion now works correctly: both ::ffff:a.b.c.d and raw hex forms like 00:00:00:00:00:ffff:c0a8:0101 are recognized and mapped back to a.b.c.d.
Round-trip conversion (IPv4 → IPv6 → IPv4) is now correct and lossless.

Motivation & linked issue

Fixes: Broken IPv6 ↔ IPv4 conversions in mapcidr.

Problem:
- Inputs like 00:00:00:00:00:192.168.1.1 could not be parsed back to IPv4.
- Inputs like 00:00:00:00:00:ffff:c0a8:0101 could not be parsed back to IPv4.
Expected:
- ToIP4("::ffff:192.168.1.1") → 192.168.1.1
- ToIP4("00:00:00:00:00:ffff:c0a8:0101") → 192.168.1.1

Issues

ToIP4 failed to parse hex-form IPv6 literals into IPv4.
Round-trip conversions were inconsistent.

Improvements

ToIP4 can parse both hex-form and ::ffff:-style mapped addresses.
Bidirectional consistency guaranteed: IPv4 → IPv6 → IPv4 yields the same IPv4.

CLI examples

IPv6 (hex) → IPv4

echo ::ffff:c0a8:0101 | mapcidr -t4
# Before: malformed output(bug)
# After : 192.168.1.1

IPv6 (::ffff mapped) → IPv4

echo ::ffff:192.168.1.1 | mapcidr -t4
# Before: malformed output(bug)
# After : 192.168.1.1

Round-trip

echo 192.168.1.1 | mapcidr -t6 | mapcidr -t4
# Before: malformed output(bug)
# After : 192.168.1.1

Test

[Problem 1]

=> This bug has a colon, but it is recognized as ipv4 (fixed in main.go)

[Problem 2 (After Problem1 fix)]

=> This bug occurs in the logic that adds unconditionally without verifying the IP format.

[1,2 > Solution]

[Problem 3]

[3 > Solution]

Summary by CodeRabbit

Bug Fixes
- Correctly append /32 for IPv4 and /128 for IPv6 when processing single IP inputs.
- Ensure IPv4 addresses in ranges are consistently represented as IPv4‑mapped IPv6 where applicable.
- Improve IPv4↔IPv6 conversion accuracy, including support for ::ffff formats and round-trips.
Tests
- Added integration tests covering IPv6/IPv4 conversions and round‑trip cases for mapped (::ffff) and hex formats.

parameter naming fix

coderabbitai · 2025-09-24T22:06:56Z

Walkthrough

Adds new IPv4/IPv6 conversion integration tests; adjusts CLI logic to append /32 or /128 to single IP inputs based on presence of ":"; updates ipNetToRange to map first and last IPv4 addresses to IPv4-mapped IPv6 form whenever To4() is non-nil.

Changes

Cohort / File(s)	Summary
Integration tests: IPv4/IPv6 conversions `cmd/integration-test/mapcidr.go`	Adds test cases covering IPv6-mapped IPv4 inputs and round-trip conversions between IPv4 and IPv6-mapped forms using -t4 and -t6.
CLI single-IP CIDR suffix logic `cmd/mapcidr/main.go`	Replaces type-switch with string-based check: append /32 when no colon is present (IPv4), else /128 (IPv6); modifies control flow for standalone IP handling.
IP range mapping adjustments `ip.go`	Simplifies ipNetToRange to map firstIP and lastIP to IPv4-mapped IPv6 whenever To4() is non-nil; separates conditions for first and last IP mappings.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant U as User
  participant CLI as mapcidr (main)
  participant IP as ipNetToRange

  U->>CLI: Provide input (IP or CIDR) with target (-t4 / -t6)
  alt Input is single IP
    CLI->>CLI: Check for ":" in input
    alt No ":" (IPv4)
      CLI->>CLI: Append /32
    else Has ":" (IPv6)
      CLI->>CLI: Append /128
    end
  end

  CLI->>IP: Compute range from CIDR
  note over IP: If firstIP.To4()!=nil → map to ::ffff:...<br/>If lastIP.To4()!=nil → map to ::ffff:...
  IP-->>CLI: First/Last IP (possibly IPv4-mapped IPv6)
  CLI-->>U: Output converted addresses

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

fix: correctly filter IPs from CIDR during aggregation #684 — Also modifies ip.go’s ipNetToRange IPv4-to-IPv6 mapping conditions, suggesting overlap in address mapping behavior changes.

Poem

A hop, a skip, through colons and dots,
I nibble at bits in mapped garden plots.
/32 here, /128 there—
Carrots of tests in meticulous care.
From v4 to v6, I bound with delight,
Ears up for ranges that now map just right. 🥕🐇

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run `@coderabbitai generate docstrings` to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title accurately describes the primary change of correcting IP conversion functions to handle IPv4-mapped IPv6 formats and aligns with the content of the pull request, making it clear to reviewers what is being addressed. It is concise, focused on the core functionality update, and avoids irrelevant details. The inclusion of the issue reference does not detract from its clarity.

✨ Finishing touches

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Actionable comments posted: 0

🧹 Nitpick comments (1)

cmd/integration-test/mapcidr.go (1)

86-93: New IPv6↔IPv4 conversion tests — LGTM.

Solid coverage for hex and ::ffff forms and roundtrip. Consider adding a filter case with -fi ::ffff:192.168.1.1 to ensure only a single host is filtered (see main.go comment about /32 vs /128 consistency).

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between f63ba9a and 4798974.

📒 Files selected for processing (3)

cmd/integration-test/mapcidr.go (1 hunks)
cmd/mapcidr/main.go (1 hunks)
ip.go (1 hunks)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (2)

GitHub Check: Test Builds
GitHub Check: Analyze (go)

🔇 Additional comments (2)

ip.go (1)

282-287: Map both ends of IPv4 ranges to v4-mapped IPv6 — LGTM; verify coalescing.

Making both first and last IPv4 endpoints v4-mapped ensures consistent width and fixes edge joins. Looks good. Please sanity-check coalescing/partition flows for small IPv4 CIDRs to ensure no regression in range math.
cmd/mapcidr/main.go (1)
393-397: Unify single-IP CIDR suffix in cidrsToNetworks

In cmd/mapcidr/main.go’s cidrsToNetworks, replace the existing To4() check with the colon-aware logic used in process to prevent treating IPv4-mapped IPv6 as /32:
-				if ip.To4() != nil {
-					cidr += "/32"
-				} else {
-					cidr += "/128"
-				}
+				if ip.To4() != nil && !strings.Contains(cidr, ":") {
+					cidr += "/32"
+				} else {
+					cidr += "/128"
+				}
Optional: add an integration test for filtering a single host via -fi ::ffff:192.168.1.1.

Likely an incorrect or invalid review comment.

s-cu-bot and others added 2 commits September 20, 2025 16:11

Fixed IP Address Conversion Issue

76ed959

Update ip.go

2773936

parameter naming fix

s-cu-bot mentioned this pull request Sep 20, 2025

Fix IP Address Conversion Functions for Proper IPv4-Mapped IPv6 Format #641

Closed

dogancanbakir requested review from Mzack9999 and dwisiswant0 September 22, 2025 13:46

adding integration tests

4798974

Mzack9999 linked an issue Sep 24, 2025 that may be closed by this pull request

Fix IP Address Conversion Functions for Proper IPv4-Mapped IPv6 Format #641

Closed

Mzack9999 approved these changes Sep 24, 2025

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Mzack9999 merged commit 56c7bcd into projectdiscovery:main Sep 24, 2025
6 of 7 checks passed

coderabbitai bot reviewed Sep 24, 2025

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BrewTestBot mentioned this pull request Oct 7, 2025

mapcidr 1.1.96 Homebrew/homebrew-core#247209

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Comments

[Fix] IP Address Conversion Functions for Proper IPv4-Mapped IPv6 Format (Issue #641)#690

[Fix] IP Address Conversion Functions for Proper IPv4-Mapped IPv6 Format (Issue #641)#690
Mzack9999 merged 3 commits intoprojectdiscovery:mainfrom
s-cu-bot:main

s-cu-bot commented Sep 20, 2025 •

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s-cu-bot commented Sep 20, 2025 • edited by coderabbitai bot Loading Uh oh! There was an error while loading. Please reload this page.

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Fix IPv6 → IPv4 Conversion and Adjust IPv4-to-IPv6 Mapping Format

Summary

Motivation & linked issue

Issues

Improvements

CLI examples

IPv6 (hex) → IPv4

IPv6 (::ffff mapped) → IPv4

Round-trip

Test

Summary by CodeRabbit

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coderabbitai bot commented Sep 24, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Walkthrough

Changes

Sequence Diagram(s)

Estimated code review effort

Possibly related PRs

Poem

Pre-merge checks and finishing touches

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s-cu-bot commented Sep 20, 2025 •

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coderabbitai bot commented Sep 24, 2025 •

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