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dhcpd: imp docs

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This commit is contained in:
Eugene Burkov
2025-03-07 13:01:34 +03:00
parent 777b310a4b
commit 4b0db6d397
1 changed files with 12 additions and 7 deletions
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19
internal/dhcpd/routeradv.go
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@@ -69,10 +69,11 @@ type icmpv6RA struct {
mtu uint32
}
// hwAddrToLinkLayerAddr converts a hardware address into a form required by
// RFC4861. That is, a byte slice of length divisible by 8.
// hwAddrToLinkLayerAddr clones the hardware address and returns it as a byte
// slice suitable for the Source Link-Layer Address option in the ICMPv6
// Router Advertisement packet.
//
// See https://tools.ietf.org/html/rfc4861#section-4.6.1.
// TODO(e.burkov): Check if it's safe to use the original slice.
func hwAddrToLinkLayerAddr(hwa net.HardwareAddr) (lla []byte, err error) {
err = netutil.ValidateMAC(hwa)
if err != nil {
@@ -81,7 +82,6 @@ func hwAddrToLinkLayerAddr(hwa net.HardwareAddr) (lla []byte, err error) {
return nil, err
}
// TODO(e.burkov): Check if it's safe to use the original slice.
return slices.Clone(hwa), nil
}
@@ -125,16 +125,21 @@ func hwAddrToLinkLayerAddr(hwa net.HardwareAddr) (lla []byte, err error) {
func createICMPv6RAPacket(params icmpv6RA) (data []byte, err error) {
lla, err := hwAddrToLinkLayerAddr(params.sourceLinkLayerAddress)
if err != nil {
return nil, fmt.Errorf("converting source link layer address: %w", err)
return nil, fmt.Errorf("converting source link-layer address: %w", err)
}
// Calculate length of the source link-layer address option.
// Calculate length of the source link-layer address option. As per RFC
// 4861, section 4.6.1, the length should be in units of 8 octets, including
// the type and length fields.
//
// See https://datatracker.ietf.org/doc/html/rfc4861#section-4.6.1.
srcLLAOptLen := len(lla) + 2
// Make sure the value is rounded up to the nearest multiple of 8.
srcLLAOptLenValue := (srcLLAOptLen + 7) / 8
srcLLAPadLen := srcLLAOptLenValue*8 - srcLLAOptLen
// TODO(a.garipov): Don't use a magic constant here. Refactor the code
// and make all constants named instead of all those comments..
// and make all constants named instead of all those comments.
data = make([]byte, 80+srcLLAOptLen+srcLLAPadLen)
i := 0