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Kernel: Use correct destination MAC address for multicast packets

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Previously we'd incorrectly use the default gateway's MAC address.
Instead we must use destination MAC addresses that are derived from
the multicast IPv4 address.

With this patch applied I can query mDNS on a real network.
This commit is contained in:
Gunnar Beutner 2021-05-07 18:55:42 +02:00 • committed by Andreas Kling
parent a569381037
commit c160c6b035
1 changed files with 8 additions and 0 deletions
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8
Kernel/Net/Routing.cpp
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@ -122,6 +122,11 @@ bool RoutingDecision::is_zero() const
return adapter.is_null() || next_hop.is_zero(); return adapter.is_null() || next_hop.is_zero();
} }
static MACAddress multicast_ethernet_address(IPv4Address const& address)
{
return MACAddress { 0x01, 0x00, 0x5e, (u8)(address[1] & 0x7f), address[2], address[3] };
}
RoutingDecision route_to(const IPv4Address& target, const IPv4Address& source, const RefPtr<NetworkAdapter> through) RoutingDecision route_to(const IPv4Address& target, const IPv4Address& source, const RefPtr<NetworkAdapter> through)
{ {
auto matches = [&](auto& adapter) { auto matches = [&](auto& adapter) {
@ -198,6 +203,9 @@ RoutingDecision route_to(const IPv4Address& target, const IPv4Address& source, c
if (target_addr == 0xffffffff && matches(adapter)) if (target_addr == 0xffffffff && matches(adapter))
return { adapter, { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff } }; return { adapter, { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff } };
if ((target_addr & IPv4Address { 240, 0, 0, 0 }.to_u32()) == IPv4Address { 224, 0, 0, 0 }.to_u32())
return { adapter, multicast_ethernet_address(target) };
{ {
Locker locker(arp_table().lock()); Locker locker(arp_table().lock());
auto addr = arp_table().resource().get(next_hop_ip); auto addr = arp_table().resource().get(next_hop_ip);