wehub-resource-sync
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69 lines
3.0 KiB
Swift
69 lines
3.0 KiB
Swift
//===----------------------------------------------------------------------===//
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// Copyright © 2026 Apple Inc. and the Containerization project authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//===----------------------------------------------------------------------===//
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import Foundation
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/// Reads the host's default IPv4 egress interface from `/proc/net/route`.
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///
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/// `/proc/net/route` columns (tab-separated):
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///
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/// Iface Destination Gateway Flags RefCnt Use Metric Mask MTU Window IRTT
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///
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/// Numeric fields are hex with bytes in network order (so `0102A8C0` is
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/// `192.168.2.1`). Pure-string parsing keeps this cross-platform-testable
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/// even though `/proc/net/route` itself only exists on Linux.
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enum HostDefaultRoute {
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/// `RTF_GATEWAY` from `<linux/route.h>`. Set on rows representing a gateway route.
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private static let RTF_GATEWAY: UInt32 = 0x0002
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/// Parse the contents of `/proc/net/route` and return the iface for the
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/// default route (destination 0.0.0.0 with `RTF_GATEWAY`). When multiple
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/// default routes exist, the one with the lowest metric wins.
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static func parseEgress(procNetRoute contents: String) -> String? {
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var best: (iface: String, metric: UInt64)?
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for (i, line) in contents.split(separator: "\n", omittingEmptySubsequences: true).enumerated() {
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if i == 0 { continue } // header
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let cols = line.split(separator: "\t", omittingEmptySubsequences: false)
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.map { $0.trimmingCharacters(in: .whitespaces) }
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guard cols.count >= 11 else { continue }
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let iface = String(cols[0])
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let destination = cols[1]
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let flagsHex = cols[3]
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let metricStr = cols[6]
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guard destination == "00000000" else { continue }
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guard let flags = UInt32(flagsHex, radix: 16),
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flags & RTF_GATEWAY != 0
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else { continue }
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let metric = UInt64(metricStr) ?? UInt64.max
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if let current = best, metric >= current.metric {
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continue
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}
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best = (iface, metric)
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}
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return best?.iface
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}
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/// Read `/proc/net/route` and return the default-route iface, or nil if
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/// the file is missing or no default route exists.
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static func currentEgress() -> String? {
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guard let contents = try? String(contentsOfFile: "/proc/net/route", encoding: .utf8) else {
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return nil
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}
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return parseEgress(procNetRoute: contents)
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}
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}
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