all: sync with master; upd chlog

internal/dhcpd/conn_unix.go

@@ -1,4 +1,4 @@
-//go:build darwin || freebsd || linux || openbsd
+//go:build freebsd || linux || openbsd
 
 package dhcpd
 
@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/netutil"
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
@@ -238,3 +239,53 @@ func (c *dhcpConn) buildEtherPkt(payload []byte, peer *dhcpUnicastAddr) (pkt []b
 
 	return buf.Bytes(), nil
 }
+
+// send writes resp for peer to conn considering the req's parameters 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) {
+	switch giaddr, ciaddr, mtype := req.GatewayIPAddr, req.ClientIPAddr, resp.MessageType(); {
+	case giaddr != nil && !giaddr.IsUnspecified():
+		// 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,
+		}
+		if mtype == dhcpv4.MessageTypeNak {
+			// Set the broadcast bit in the DHCPNAK, so that the relay agent
+			// broadcasts it to the client, because the client may not have
+			// a correct network address or subnet mask, and the client may not
+			// be answering ARP requests.
+			resp.SetBroadcast()
+		}
+	case mtype == dhcpv4.MessageTypeNak:
+		// Broadcast any DHCPNAK messages to 0xffffffff.
+	case ciaddr != nil && !ciaddr.IsUnspecified():
+		// Unicast DHCPOFFER and DHCPACK messages to the address in
+		// ciaddr.
+		peer = &net.UDPAddr{
+			IP:   ciaddr,
+			Port: dhcpv4.ClientPort,
+		}
+	case !req.IsBroadcast() && req.ClientHWAddr != nil:
+		// Unicast DHCPOFFER and DHCPACK messages to the client's
+		// hardware address and yiaddr.
+		peer = &dhcpUnicastAddr{
+			Addr:   packet.Addr{HardwareAddr: req.ClientHWAddr},
+			yiaddr: resp.YourIPAddr,
+		}
+	default:
+		// Go on since peer is already set to broadcast.
+	}
+
+	pktData := resp.ToBytes()
+
+	log.Debug("dhcpv4: sending %d bytes to %s: %s", len(pktData), peer, resp.Summary())
+
+	_, err := conn.WriteTo(pktData, peer)
+	if err != nil {
+		log.Error("dhcpv4: conn.Write to %s failed: %s", peer, err)
+	}
+}