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Kernel: Hold less locks when receiving ICMP packets

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* We don't have to lock the "all IPv4 sockets" in exclusive mode, shared mode is
  enough for just reading the list (as opposed to modifying it).
* We don't have to lock socket's own lock at all, the IPv4Socket::did_receive()
  implementation takes care of this.
* Most importantly, we don't have to hold the "all IPv4 sockets" across the
  IPv4Socket::did_receive() call(s). We can copy the current ICMP socket list
  while holding the lock, then release the lock, and then call
  IPv4Socket::did_receive() on all the ICMP sockets in our list.

These changes fix a deadlock triggered by receiving ICMP messages when using tap
networking setup (as opposed to QEMU's default user/SLIRP networking) on the host.
This commit is contained in:
Sergey Bugaev 2021-02-12 16:49:34 +03:00 committed by Andreas Kling
parent ffa39f98e8
commit 4717009e3e
1 changed files with 10 additions and 6 deletions
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16
Kernel/Net/NetworkTask.cpp
View file

@ -250,13 +250,17 @@ void handle_icmp(const EthernetFrameHeader& eth, const IPv4Packet& ipv4_packet,
#endif
{
LOCKER(IPv4Socket::all_sockets().lock());
for (RefPtr<IPv4Socket> socket : IPv4Socket::all_sockets().resource()) {
LOCKER(socket->lock());
if (socket->protocol() != (unsigned)IPv4Protocol::ICMP)
continue;
socket->did_receive(ipv4_packet.source(), 0, KBuffer::copy(&ipv4_packet, sizeof(IPv4Packet) + ipv4_packet.payload_size()), packet_timestamp);
NonnullRefPtrVector<IPv4Socket> icmp_sockets;
{
LOCKER(IPv4Socket::all_sockets().lock(), Lock::Mode::Shared);
for (auto* socket : IPv4Socket::all_sockets().resource()) {
if (socket->protocol() != (unsigned)IPv4Protocol::ICMP)
continue;
icmp_sockets.append(*socket);
}
}
for (auto& socket : icmp_sockets)
socket.did_receive(ipv4_packet.source(), 0, KBuffer::copy(&ipv4_packet, sizeof(IPv4Packet) + ipv4_packet.payload_size()), packet_timestamp);
}
auto adapter = NetworkAdapter::from_ipv4_address(ipv4_packet.destination());