talos

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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package nethelpers
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import (
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	"crypto/sha256"
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	"fmt"
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)
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const maxLinkNameLength = 15
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// VLANLinkName builds a VLAN link name out of the base device name and VLAN ID.
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//
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// The function takes care of the maximum length of the link name.
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func VLANLinkName(base string, vlanID uint16) string {
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	// VLAN ID is actually 12-bit, so the allowed values are 0-4095.
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	// In ".%d" format, vlanID can be up to 5 characters long.
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	if len(base)+5 <= maxLinkNameLength {
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		return fmt.Sprintf("%s.%d", base, vlanID)
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	}
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	// If the base name is too long, we need to truncate it, but simply
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	// truncating might lead to ambiguous link name, so take some hash of the original
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	// name.
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	prefix := base[:4]
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	hash := sha256.Sum256([]byte(base))
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	return fmt.Sprintf("%s%x.%d", prefix, hash[:(maxLinkNameLength-len(prefix)-5)/2], vlanID)
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}
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