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Pull request: 3443 dhcp broadcast

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Merge in DNS/adguard-home from 3443-fix-wired-dhcp to master

Updates #3443.

Squashed commit of the following:

commit ec7c3b73e274ba7c05c5856cb2f4ea218ad46870
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Sep 7 18:21:07 2021 +0300

    dhcpd: imp docs & naming

commit d87c646af44d837c81aa032e82aad846bde97bc8
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Sep 7 16:56:36 2021 +0300

    dhcpd: fix build tags & log changes

commit cbd0b3c1aa0efb32aeaa9130111719ab3861e817
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Sep 7 16:26:50 2021 +0300

    dhcpd: revert 3443 & imp broadcasting
This commit is contained in:
Eugene Burkov
2021-09-07 18:33:23 +03:00
parent bdd0ca5423
commit b77ceaaf55
8 changed files with 404 additions and 17 deletions
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56
internal/dhcpd/v4.go
View File

@@ -928,28 +928,50 @@ func (s *v4Server) packetHandler(conn net.PacketConn, peer net.Addr, req *dhcpv4
resp.Options.Update(dhcpv4.OptMessageType(dhcpv4.MessageTypeNak))
}
// peer is expected to be of type *net.UDPConn as the server4.NewServer
// initializes it.
udpPeer, ok := peer.(*net.UDPAddr)
if !ok {
log.Error("dhcpv4: peer is of unexpected type %T", peer)
s.send(peer, conn, req, resp)
}
// send writes resp for peer to conn considering the req's fields and options
// according to RFC-2131.
//
// See https://datatracker.ietf.org/doc/html/rfc2131#section-4.1.
func (s *v4Server) send(peer net.Addr, conn net.PacketConn, req, resp *dhcpv4.DHCPv4) {
var unicast bool
if giaddr, unspec := req.GatewayIPAddr, netutil.IPv4Zero(); !giaddr.Equal(unspec) {
// Send any return messages to the server port on the BOOTP
// relay agent whose address appears in giaddr.
peer = &net.UDPAddr{
IP: giaddr,
Port: dhcpv4.ServerPort,
}
unicast = true
} else if mtype := resp.MessageType(); mtype == dhcpv4.MessageTypeNak {
// Broadcast any DHCPNAK messages to 0xffffffff.
} else if ciaddr := req.ClientIPAddr; !ciaddr.Equal(unspec) {
// Unicast DHCPOFFER and DHCPACK messages to the address in
// ciaddr.
peer = &net.UDPAddr{
IP: ciaddr,
Port: dhcpv4.ClientPort,
}
unicast = true
}
// TODO(e.burkov): Unicast the message to the actual link-layer address
// of the client if broadcast bit is not set. Perhaps, use custom
// connection when creating the server.
//
// See https://github.com/AdguardTeam/AdGuardHome/issues/3443.
if !unicast {
s.broadcast(peer, conn, resp)
return
}
// Despite the fact that server4.NewIPv4UDPConn explicitly sets socket
// options to allow broadcasting, it also binds the connection to a
// specific interface. On FreeBSD conn.WriteTo causes errors while
// writing to the addresses that belong to another interface. So, use
// the broadcast address specific for the binded interface in case
// server4.Server.Serve sets it to net.IPv4Bcast.
if udpPeer.IP.Equal(net.IPv4bcast) {
udpPeer.IP = s.conf.broadcastIP
}
log.Debug("dhcpv4: sending to %s: %s", peer, resp.Summary())
log.Debug("dhcpv4: sending: %s", resp.Summary())
_, err = conn.WriteTo(resp.ToBytes(), peer)
_, err := conn.WriteTo(resp.ToBytes(), peer)
if err != nil {
log.Error("dhcpv4: conn.Write to %s failed: %s", peer, err)
}