fixed fallback for non io_uring packet send/recv

cert/pem.go

@@ -1,6 +1,7 @@
 package cert
 
 import (
+	"encoding/hex"
 	"encoding/pem"
 	"fmt"
 	"time"
@@ -249,9 +250,11 @@ func UnmarshalNebulaCertificateFromPEM(b []byte) (*NebulaCertificate, []byte, er
 
 	// Handle issuer
 	if c.Issuer() != "" {
-		// Convert hex string fingerprint back to bytes (this is an approximation)
+		issuerBytes, err := hex.DecodeString(c.Issuer())
-		// The old API used raw bytes, new API uses hex string
+		if err != nil {
-		nc.Details.Issuer = []byte(c.Issuer())
+			return nil, rest, fmt.Errorf("failed to decode issuer fingerprint: %w", err)
+		}
+		nc.Details.Issuer = issuerBytes
 	}
 
 	return nc, rest, nil

udp/udp_linux.go

@@ -1628,6 +1628,57 @@ func isEAgain(err error) bool {
 	return false
 }
 
+func (u *StdConn) readSingleSyscall(msgs []rawMessage) (int, error) {
+	if len(msgs) == 0 {
+		return 0, nil
+	}
+	for {
+		n, _, errno := unix.Syscall6(
+			unix.SYS_RECVMSG,
+			uintptr(u.sysFd),
+			uintptr(unsafe.Pointer(&msgs[0].Hdr)),
+			0,
+			0,
+			0,
+			0,
+		)
+		if errno != 0 {
+			err := syscall.Errno(errno)
+			if err == unix.EINTR {
+				continue
+			}
+			return 0, &net.OpError{Op: "recvmsg", Err: err}
+		}
+		msgs[0].Len = uint32(n)
+		return 1, nil
+	}
+}
+
+func (u *StdConn) readMultiSyscall(msgs []rawMessage) (int, error) {
+	if len(msgs) == 0 {
+		return 0, nil
+	}
+	for {
+		n, _, errno := unix.Syscall6(
+			unix.SYS_RECVMMSG,
+			uintptr(u.sysFd),
+			uintptr(unsafe.Pointer(&msgs[0])),
+			uintptr(len(msgs)),
+			unix.MSG_WAITFORONE,
+			0,
+			0,
+		)
+		if errno != 0 {
+			err := syscall.Errno(errno)
+			if err == unix.EINTR {
+				continue
+			}
+			return 0, &net.OpError{Op: "recvmmsg", Err: err}
+		}
+		return int(n), nil
+	}
+}
+
 func (u *StdConn) ReadSingle(msgs []rawMessage) (int, error) {
 	if len(msgs) == 0 {
 		return 0, nil
@@ -1637,8 +1688,7 @@ func (u *StdConn) ReadSingle(msgs []rawMessage) (int, error) {
 
 	state := u.ioState.Load()
 	if state == nil {
-		u.l.Error("ReadSingle: io_uring not initialized")
+		return u.readSingleSyscall(msgs)
-		return 0, &net.OpError{Op: "recvmsg", Err: errors.New("io_uring not initialized")}
 	}
 
 	u.l.Debug("ReadSingle: converting rawMessage to unix.Msghdr")
@@ -1679,8 +1729,7 @@ func (u *StdConn) ReadMulti(msgs []rawMessage) (int, error) {
 
 	state := u.ioState.Load()
 	if state == nil {
-		u.l.Error("ReadMulti: io_uring not initialized")
+		return u.readMultiSyscall(msgs)
-		return 0, &net.OpError{Op: "recvmsg", Err: errors.New("io_uring not initialized")}
 	}
 
 	count := 0
@@ -2176,7 +2225,14 @@ func (u *StdConn) directWrite(b []byte, addr netip.AddrPort) error {
 		"remote_is_v6": addr.Addr().Is6(),
 	}).Debug("io_uring directWrite invoked")
 	if state == nil {
-		return errors.New("io_uring state unavailable")
+		written, err := u.sendMsgSync(addr, b, nil, 0)
+		if err != nil {
+			return err
+		}
+		if written != len(b) {
+			return fmt.Errorf("sendmsg short write: wrote %d expected %d", written, len(b))
+		}
+		return nil
 	}
 	n, err := u.sendMsgIOUring(state, addr, b, nil, 0)
 	if err != nil {