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core/dnsserver: preserve UDP packet destination addresses (#8644)

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* core/dnsserver: preserve UDP packet destination addresses

Signed-off-by: houyuwushang <180804215+houyuwushang@users.noreply.github.com>

* test: modernize reverse UDP reply traversal

Signed-off-by: houyuwushang <180804215+houyuwushang@users.noreply.github.com>

* test: account for Unix IPv4 source-control capabilities

Signed-off-by: houyuwushang <180804215+houyuwushang@users.noreply.github.com>

---------

Signed-off-by: houyuwushang <180804215+houyuwushang@users.noreply.github.com>
This commit is contained in:
houyuwushang
2026-10-21 11:34:18 +08:00
committed by GitHub
parent e7f823b261
commit 0fe7b08fbb
12 changed files with 1026 additions and 3 deletions
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45
core/dnsserver/udp_unix.go Normal file
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@@ -0,0 +1,45 @@
//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
package dnsserver
import (
"net"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"golang.org/x/sys/unix"
)
var udpOOBSize = len(ipv4.NewControlMessage(ipv4.FlagDst|ipv4.FlagInterface)) +
len(ipv6.NewControlMessage(ipv6.FlagDst|ipv6.FlagInterface))
func enableUDPPacketInfo(conn *net.UDPConn) bool {
err4 := ipv4.NewPacketConn(conn).SetControlMessage(ipv4.FlagDst|ipv4.FlagInterface, true)
err6 := ipv6.NewPacketConn(conn).SetControlMessage(ipv6.FlagDst|ipv6.FlagInterface, true)
return err4 == nil || err6 == nil
}
func parseUDPPacketInfo(oob []byte, flags int) udpPacketInfo {
if flags&unix.MSG_CTRUNC != 0 {
return udpPacketInfo{}
}
cm6 := new(ipv6.ControlMessage)
if cm6.Parse(oob) == nil && cm6.Dst != nil {
return udpPacketInfo{dst: cm6.Dst, ifIndex: cm6.IfIndex}
}
cm4 := new(ipv4.ControlMessage)
if cm4.Parse(oob) == nil && cm4.Dst != nil {
return udpPacketInfo{dst: cm4.Dst, ifIndex: cm4.IfIndex}
}
return udpPacketInfo{}
}
func udpSourceControl(info udpPacketInfo) []byte {
if info.dst == nil || info.dst.IsUnspecified() || info.dst.IsMulticast() {
return nil
}
if ip4 := info.dst.To4(); ip4 != nil {
return (&ipv4.ControlMessage{Src: ip4, IfIndex: info.replyInterface()}).Marshal()
}
return (&ipv6.ControlMessage{Src: info.dst, IfIndex: info.replyInterface()}).Marshal()
}