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Only use first 3 DHCP advertised DNS servers. 

The OPT_DOMAIN_NAME_SERVER DHCP option field can advertise an unbounded
DNS servers, but we currently use a fixed length array to store these
servers. This commit ensures only the first 3 (highest priority) servers
are used.

Fixes #305.
This commit is contained in:
Chris Ballance 2019-09-30 18:19:05 +01:00 committed by whitequark
parent 186bc05d77
commit 0df7e51a9f
1 changed files with 38 additions and 1 deletions
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39
src/wire/dhcpv4.rs
View File

@ -742,7 +742,7 @@ impl<'a> Repr<'a> {
}
DhcpOption::Other {kind: field::OPT_DOMAIN_NAME_SERVER, data} => {
let mut dns_servers_inner = [None; 3];
for i in 0.. {
for i in 0..3 {
let offset = 4 * i;
let end = offset + 4;
if end > data.len() { break }
@ -840,6 +840,30 @@ mod test {
0x00, 0x00, 0x37, 0x04, 0x01, 0x03, 0x06, 0x2a, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];
static ACK_BYTES: &[u8] = &[
0x02, 0x01, 0x06, 0x00, 0xcc, 0x34, 0x75, 0xab, 0x00, 0x00, 0x80, 0x00, 0x0a, 0xff, 0x06, 0x91,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0xff, 0x06, 0xfe, 0x34, 0x17, 0xeb, 0xc9,
0xaa, 0x2f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x63, 0x82, 0x53, 0x63,
0x35, 0x01, 0x05, 0x36, 0x04, 0xa3, 0x01, 0x4a, 0x16, 0x01, 0x04, 0xff, 0xff, 0xff, 0x00, 0x2b,
0x05, 0xdc, 0x03, 0x4e, 0x41, 0x50, 0x0f, 0x15, 0x6e, 0x61, 0x74, 0x2e, 0x70, 0x68, 0x79, 0x73,
0x69, 0x63, 0x73, 0x2e, 0x6f, 0x78, 0x2e, 0x61, 0x63, 0x2e, 0x75, 0x6b, 0x00, 0x03, 0x04, 0x0a,
0xff, 0x06, 0xfe, 0x06, 0x10, 0xa3, 0x01, 0x4a, 0x06, 0xa3, 0x01, 0x4a, 0x07, 0xa3, 0x01, 0x4a,
0x03, 0xa3, 0x01, 0x4a, 0x04, 0x2c, 0x10, 0xa3, 0x01, 0x4a, 0x03, 0xa3, 0x01, 0x4a, 0x04, 0xa3,
0x01, 0x4a, 0x06, 0xa3, 0x01, 0x4a, 0x07, 0x2e, 0x01, 0x08, 0xff
];
const IP_NULL: Ipv4Address = Ipv4Address([0, 0, 0, 0]);
const CLIENT_MAC: EthernetAddress = EthernetAddress([0x0, 0x0b, 0x82, 0x01, 0xfc, 0x42]);
@ -979,4 +1003,17 @@ mod test {
assert_eq!(&bytes[0..2], &[field::OPT_PARAMETER_REQUEST_LIST, DATA.len() as u8]);
assert_eq!(&bytes[2..], DATA);
}
#[test]
fn test_parse_ack_dns_servers() {
let packet = Packet::new_unchecked(ACK_BYTES);
let repr = Repr::parse(&packet).unwrap();
// The packet described by ACK_BYTES advertises 4 DNS servers
// Here we ensure that we correctly parse the first 3 into our fixed
// length-3 array (see issue #305)
assert_eq!(repr.dns_servers, Some([
Some(Ipv4Address([163, 1, 74, 6])),
Some(Ipv4Address([163, 1, 74, 7])),
Some(Ipv4Address([163, 1, 74, 3]))]));
}
}