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dhcpd: Fix slaac configuration which was not working due to invalid icmp packet

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Signed-off-by: Gunjan Gupta <viraniac@gmail.com>
This commit is contained in:
Gunjan Gupta
2025-01-03 20:52:31 +05:30
parent 0b25119c52
commit b1657c2b2a
2 changed files with 13 additions and 17 deletions
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23
internal/dhcpd/routeradv.go
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@@ -50,16 +50,7 @@ func hwAddrToLinkLayerAddr(hwa net.HardwareAddr) (lla []byte, err error) {
return nil, err
}
if len(hwa) == 6 || len(hwa) == 8 {
lla = make([]byte, 8)
copy(lla, hwa)
return lla, nil
}
// Assume that netutil.ValidateMAC prevents lengths other than 20 by
// now.
lla = make([]byte, 24)
lla = make([]byte, len(hwa))
copy(lla, hwa)
return lla, nil
@@ -109,9 +100,15 @@ func createICMPv6RAPacket(params icmpv6RA) (data []byte, err error) {
return nil, fmt.Errorf("converting source link layer address: %w", err)
}
// Calculate length of source link layer address section
// This is based on calculation from radvd's add_ra_option_sllao function
sllao_bytes := len(lla) + 2
sllao_len := (sllao_bytes + 7) / 8
sllao_pad_bytes := sllao_len * 8 - sllao_bytes
// TODO(a.garipov): Don't use a magic constant here. Refactor the code
// and make all constants named instead of all those comments..
data = make([]byte, 82+len(lla))
data = make([]byte, 80+sllao_bytes+sllao_pad_bytes)
i := 0
// ICMPv6:
@@ -176,11 +173,11 @@ func createICMPv6RAPacket(params icmpv6RA) (data []byte, err error) {
// Option=Source link-layer address:
data[i] = 1 // Type
data[i+1] = 1 // Length
data[i+1] = byte(sllao_len) // Length
i += 2
copy(data[i:], lla) // Link-Layer Address[8/24]
i += len(lla)
i += len(lla) + sllao_pad_bytes
// Option=Recursive DNS Server: