248 lines
8.8 KiB
Rust
248 lines
8.8 KiB
Rust
use crate::dhcp_snooper::Lease;
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use crate::proxy::udp_packet_helper::UdpPacketHelper;
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use crate::proxy::{Action, Proxy};
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use anyhow::Context;
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use anyhow::Result;
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use ipnet::Ipv4Net;
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use smoltcp::wire::{
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ArpOperation, ArpPacket, ArpRepr, EthernetFrame, EthernetProtocol, IpProtocol, Ipv4Packet,
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UdpPacket,
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};
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impl Proxy<'_> {
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pub(crate) fn process_frame_from_vm(&mut self, frame: EthernetFrame<&[u8]>) -> Result<()> {
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if self.allowed_from_vm(&frame).is_none() {
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// Block packet by not forwarding it to the host
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return Ok(());
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}
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self.host
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.write(frame.as_ref())
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.map(|_| ())
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.context("failed to write to the host")
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}
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fn allowed_from_vm(&self, frame: &EthernetFrame<&[u8]>) -> Option<()> {
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if frame.src_addr() != self.vm_mac_address {
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return None;
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}
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match frame.ethertype() {
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EthernetProtocol::Arp => {
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let arp_pkt = ArpPacket::new_checked(frame.payload()).ok()?;
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self.allowed_from_vm_arp(arp_pkt)
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}
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EthernetProtocol::Ipv4 => {
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let ipv4_pkt = Ipv4Packet::new_checked(frame.payload()).ok()?;
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self.allowed_from_vm_ipv4(ipv4_pkt)
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}
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_ => None,
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}
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}
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fn allowed_from_vm_arp(&self, arp_pkt: ArpPacket<&[u8]>) -> Option<()> {
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vm_arp_allowed(arp_pkt, self.vm_mac_address, self.dhcp_snooper.lease())
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}
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pub(crate) fn allowed_from_vm_ipv4(&self, ipv4_pkt: Ipv4Packet<&[u8]>) -> Option<()> {
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// Is this packet coming from VM's IP address that we've learned from DHCP snooping?
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if let Some(lease) = &self.dhcp_snooper.lease()
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&& lease.valid_ip_source(ipv4_pkt.src_addr())
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{
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let dst_addr = ipv4_pkt.dst_addr();
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// Filter traffic based on user-specified rules first
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if !self.rules.is_empty() {
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let dst_net = Ipv4Net::from(dst_addr);
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if let Some((_, action)) = self.rules.get_lpm(&dst_net) {
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return match action {
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Action::Allow => Some(()),
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Action::Block => None,
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};
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}
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}
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// When no user-specified rules matched, simply allow all global traffic
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if ip_network::IpNetwork::from(dst_addr).is_global() {
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return Some(());
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}
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// Additionally, allow communication with the host,
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// otherwise things like SSH to a VM won't work
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if ipv4_pkt.dst_addr() == self.host.gateway_ip {
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return Some(());
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}
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// Additionally, allow DNS requests to DNS-servers
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// provided to a VM by the host's DHCP server
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if ipv4_pkt.next_header() == IpProtocol::Udp {
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let udp_pkt = UdpPacket::new_checked(ipv4_pkt.payload()).ok()?;
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if udp_pkt.is_dns_request()
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&& self.dhcp_snooper.valid_dns_target(&ipv4_pkt.dst_addr())
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{
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return Some(());
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}
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}
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}
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// Allow outgoing DHCP requests to broadcast addresses,
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// otherwise DHCP snooper will never be populated
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if ipv4_pkt.next_header() == IpProtocol::Udp {
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let udp_pkt = UdpPacket::new_checked(ipv4_pkt.payload()).ok()?;
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// Allow DHCP communication with the bootpd(8) on host via broadcast address
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if udp_pkt.is_dhcp_request() && ipv4_pkt.dst_addr().is_broadcast() {
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return Some(());
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}
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}
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None
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}
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}
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fn vm_arp_allowed(
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arp_pkt: ArpPacket<&[u8]>,
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vm_mac_address: smoltcp::wire::EthernetAddress,
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lease: &Option<Lease>,
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) -> Option<()> {
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let (operation, source_hardware_addr, source_protocol_addr) =
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match ArpRepr::parse(&arp_pkt).ok()? {
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ArpRepr::EthernetIpv4 {
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operation,
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source_hardware_addr,
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source_protocol_addr,
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..
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} => (operation, source_hardware_addr, source_protocol_addr),
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_ => return None,
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};
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if !matches!(operation, ArpOperation::Request | ArpOperation::Reply) {
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return None;
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}
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if source_hardware_addr != vm_mac_address {
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return None;
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}
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if let Some(lease) = lease {
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if lease.valid_ip_source(source_protocol_addr) {
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return Some(());
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}
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} else if source_protocol_addr.is_unspecified() {
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return Some(());
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}
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None
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}
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#[cfg(test)]
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mod tests {
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use crate::dhcp_snooper::Lease;
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use smoltcp::wire::{
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ArpHardware, ArpOperation, ArpPacket, EthernetAddress, EthernetProtocol, Ipv4Address,
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};
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use std::collections::HashSet;
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use std::time::Duration;
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#[test]
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fn test_allowed_from_vm_arp_allows_unspecified_request_without_lease() {
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let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
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let buf = arp_packet(vm_mac_address.0, [0, 0, 0, 0], ArpOperation::Request, 6, 4);
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let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
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assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_some());
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}
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#[test]
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fn test_allowed_from_vm_arp_allows_reply_for_leased_ip() {
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let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
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let lease_ip = Ipv4Address::new(192, 168, 0, 2);
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let lease = Some(Lease::new(
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lease_ip,
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Duration::from_secs(600),
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HashSet::new(),
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));
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let buf = arp_packet(
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vm_mac_address.0,
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lease_ip.octets(),
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ArpOperation::Reply,
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6,
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4,
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);
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let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
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assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &lease).is_some());
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}
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#[test]
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fn test_allowed_from_vm_arp_rejects_unknown_operation() {
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let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
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let buf = arp_packet(
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vm_mac_address.0,
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[0, 0, 0, 0],
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ArpOperation::Unknown(3),
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6,
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4,
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);
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let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
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assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
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}
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#[test]
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fn test_allowed_from_vm_arp_rejects_non_ethernet_hardware_type() {
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let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
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let mut buf = arp_packet(vm_mac_address.0, [0, 0, 0, 0], ArpOperation::Request, 6, 4);
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let mut arp_pkt = ArpPacket::new_unchecked(buf.as_mut_slice());
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arp_pkt.set_hardware_type(ArpHardware::Unknown(2));
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let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
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assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
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}
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#[test]
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fn test_allowed_from_vm_arp_rejects_non_ipv4_protocol_type() {
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let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
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let mut buf = arp_packet(vm_mac_address.0, [0, 0, 0, 0], ArpOperation::Request, 6, 4);
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let mut arp_pkt = ArpPacket::new_unchecked(buf.as_mut_slice());
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arp_pkt.set_protocol_type(EthernetProtocol::Ipv6);
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let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
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assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
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}
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#[test]
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fn test_allowed_from_vm_arp_rejects_non_ipv4_protocol_length() {
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let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
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let buf = arp_packet(vm_mac_address.0, [0, 0, 0], ArpOperation::Request, 6, 3);
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let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
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assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
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}
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fn arp_packet(
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source_hardware_addr: [u8; 6],
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source_protocol_addr: impl AsRef<[u8]>,
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operation: ArpOperation,
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hardware_len: u8,
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protocol_len: u8,
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) -> Vec<u8> {
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let source_protocol_addr = source_protocol_addr.as_ref();
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let payload_len = 8 + 2 * (hardware_len as usize + protocol_len as usize);
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let mut buf = vec![0; payload_len];
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let mut arp_pkt = ArpPacket::new_unchecked(buf.as_mut_slice());
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arp_pkt.set_hardware_type(ArpHardware::Ethernet);
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arp_pkt.set_protocol_type(EthernetProtocol::Ipv4);
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arp_pkt.set_hardware_len(hardware_len);
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arp_pkt.set_protocol_len(protocol_len);
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arp_pkt.set_operation(operation);
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arp_pkt.set_source_hardware_addr(&source_hardware_addr[..hardware_len as usize]);
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arp_pkt.set_source_protocol_addr(source_protocol_addr);
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arp_pkt.set_target_hardware_addr(&[0; 6][..hardware_len as usize]);
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arp_pkt.set_target_protocol_addr(&vec![0; protocol_len as usize]);
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buf
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}
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}
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