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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
View File

@@ -50,16 +50,7 @@ func hwAddrToLinkLayerAddr(hwa net.HardwareAddr) (lla []byte, err error) {
return nil, err return nil, err
} }
if len(hwa) == 6 || len(hwa) == 8 { lla = make([]byte, len(hwa))
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)
copy(lla, hwa) copy(lla, hwa)
return lla, nil 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) 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 // 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, 82+len(lla)) data = make([]byte, 80+sllao_bytes+sllao_pad_bytes)
i := 0 i := 0
// ICMPv6: // ICMPv6:
@@ -176,11 +173,11 @@ func createICMPv6RAPacket(params icmpv6RA) (data []byte, err error) {
// Option=Source link-layer address: // Option=Source link-layer address:
data[i] = 1 // Type data[i] = 1 // Type
data[i+1] = 1 // Length data[i+1] = byte(sllao_len) // Length
i += 2 i += 2
copy(data[i:], lla) // Link-Layer Address[8/24] copy(data[i:], lla) // Link-Layer Address[8/24]
i += len(lla) i += len(lla) + sllao_pad_bytes
// Option=Recursive DNS Server: // Option=Recursive DNS Server:

7
internal/dhcpd/routeradv_test.go
View File

@@ -17,10 +17,9 @@ func TestCreateICMPv6RAPacket(t *testing.T) {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x05, 0x01, 0x00, 0x00, 0x00, 0x00, 0x05, 0xdc, 0x05, 0x01, 0x00, 0x00, 0x00, 0x00, 0x05, 0xdc,
0x01, 0x01, 0x0a, 0x00, 0x27, 0x00, 0x00, 0x00, 0x01, 0x01, 0x0a, 0x00, 0x27, 0x00, 0x00, 0x00,
0x00, 0x00, 0x19, 0x03, 0x00, 0x00, 0x00, 0x00, 0x19, 0x03, 0x00, 0x00, 0x00, 0x00, 0x0e, 0x10,
0x0e, 0x10, 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x08, 0x00, 0x27, 0xff, 0xfe, 0x00, 0x08, 0x00, 0x27, 0xff, 0xfe, 0x00, 0x00, 0x00,
0x00, 0x00,
} }
gotData, err := createICMPv6RAPacket(icmpv6RA{ gotData, err := createICMPv6RAPacket(icmpv6RA{