Support scoped IPv6 addresses in SocketAddress.init(ipAddress:port:)#3525
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glbrntt merged 8 commits intoapple:mainfrom Mar 6, 2026
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Motivation: `SocketAddress.init(ipAddress:port:)` uses `inet_pton` to parse IP address strings. `inet_pton` does not support the `%scope` suffix used in IPv6 link-local addresses (e.g., `fe80::1%eth0`), causing these addresses to fail with `failedToParseIPString`. This forces downstream consumers like grpc-swift-nio-transport to reimplement scoped IPv6 parsing using `getaddrinfo` themselves. Modifications: When the IP address string contains a `%` character, fall back to `getaddrinfo` with `AI_NUMERICHOST` instead of `inet_pton`. This properly parses the `%scope` suffix and sets `sin6_scope_id` in the resulting `sockaddr_in6`. The scoped path is extracted into a private `_parseScopedIPv6` helper, guarded with `#if !os(Windows) && !os(WASI)`. The non-scoped `inet_pton` path is completely unchanged. Added 5 tests: named scope (`%lo`), numeric scope (`%1`), scoped vs non-scoped inequality, invalid scopes rejected, non-scoped regression. Result: `SocketAddress(ipAddress: "fe80::1%eth0", port: 80)` now succeeds and preserves the scope ID in `sin6_scope_id`. Non-scoped addresses continue to work exactly as before.
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Lukasa
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Feb 26, 2026
Lukasa
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Mar 3, 2026
macOS's getaddrinfo silently accepts empty scopes and nonexistent interface names with scope_id == 0, unlike Linux which rejects them. Add pre-validation for empty scope strings and post-validation that scope_id is nonzero. Also make scoped IPv6 tests use the actual loopback interface index instead of hardcoding 1.
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I fixed the tests |
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@Lukasa mind kicking off CI? it should pass this time. |
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the previous failures don't seem related to this pr |
This was referenced Mar 6, 2026
glbrntt
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Mar 17, 2026
## Summary This PR preserves IPv6 scope IDs (e.g., `%eth0` in `fe80::1%eth0`) when converting between gRPC and NIO socket address types. **Updated**: Now significantly simplified since swift-nio natively supports scoped IPv6 addresses as of [apple/swift-nio#3525](apple/swift-nio#3525) (merged March 6, 2026). ## Motivation IPv6 link-local addresses (`fe80::/10`) require a scope ID to identify which network interface to use. Without preservation of the scope ID, `connect()` fails with `EINVAL` on link-local addresses. ## Changes ### Scope ID Preservation (NIO → gRPC) In `NIOSocketAddress+GRPCSocketAddress.swift`, when converting from NIO's `SocketAddress` to gRPC's `SocketAddress.IPv6`: - Reads `sin6_scope_id` from the underlying `sockaddr_in6` - Uses `if_indextoname()` to convert scope ID to interface name - Appends the scope to the host string (e.g., `fe80::1` → `fe80::1%eth0`) ### Simplified Scope ID Parsing (gRPC → NIO) **Previously**: Used `getaddrinfo` with `AI_NUMERICHOST` to parse scoped IPv6 addresses since `inet_pton` doesn't support `%scope` suffixes. **Now**: Simply calls `SocketAddress.init(ipAddress:port:)` since swift-nio now natively handles scoped IPv6 addresses. This removes ~30 lines of workaround code and makes the implementation much cleaner. ## Dependencies **Requires**: swift-nio main branch (will change to a version requirement once swift-nio releases version containing #3525) Related: - swift-nio PR: apple/swift-nio#3525 - Previous grpc-swift-nio-transport PR: #146 ## Testing - ✅ Builds successfully with swift-nio main branch - ✅ Existing tests in DNSResolverTests verify scope preservation - ✅ NIOSocketAddressConversionTests verify bidirectional conversion
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Motivation
SocketAddress.init(ipAddress:port:)usesinet_ptonto parse IP address strings.inet_ptondoes not support the%scopesuffix used in IPv6 link-local addresses (e.g.,fe80::1%eth0), causing these addresses to fail withfailedToParseIPString. This forces downstream consumers like grpc-swift-nio-transport to reimplement scoped IPv6 parsing usinggetaddrinfothemselves.Related: grpc/grpc-swift-nio-transport#147
Modifications
When the IP address string contains a
%character, fall back togetaddrinfowithAI_NUMERICHOSTinstead ofinet_pton. This properly parses the%scopesuffix and setssin6_scope_idin the resultingsockaddr_in6. The scoped path is extracted into a private_parseScopedIPv6helper, guarded with#if !os(Windows) && !os(WASI). The non-scopedinet_ptonpath is completely unchanged.Added 5 tests:
fe80::1%lo) — verifiessin6_scope_idmatchesif_nametoindexfe80::1%1) — verifies numeric index parsingsin6_scope_idmeans different addresses::1still works withscope_id == 0Result
SocketAddress(ipAddress: "fe80::1%eth0", port: 80)now succeeds and preserves the scope ID insin6_scope_id. Non-scoped addresses continue to work exactly as before.Context
This came up while working on IPv6 link-local support in grpc-swift-nio-transport#146, where the workaround was to use
getaddrinfodirectly in the gRPC layer. The reviewer suggested upstreaming this to swift-nio so the workaround can be removed.