diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4b322788fc..25e5518c25 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -144,6 +144,7 @@ jobs:
         with:
           repository: hermit-os/hermit-rs
           submodules: true
+          ref: sleep-udp
       - name: Remove hermit-kernel submodule
         run: git rm -r kernel
         working-directory: .
@@ -203,54 +204,54 @@ jobs:
         if: matrix.arch == 'x86_64'
       - run: cargo +stable install cargo-careful
         if: matrix.profile == 'dev'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package hello_world
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package wasmtime-demo --features ci
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package hello_world --no-default-features --microvm
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd --smp 4
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd --no-default-virtio-features
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd --no-default-virtio-features --smp 4
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --smp 4
-        # https://github.com/hermit-os/kernel/issues/737
-        if: matrix.arch != 'aarch64'
-        # https://github.com/hermit-os/kernel/issues/1286
-        continue-on-error: ${{ matrix.arch == 'riscv64' }}
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rftrace-example --virtiofsd
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --features ci,hermit/dhcpv4 --netdev virtio-net-pci
-        if: matrix.arch != 'riscv64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --features ci,hermit/dhcpv4 --netdev virtio-net-pci --no-default-virtio-features
-        if: matrix.arch != 'riscv64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --no-default-features --microvm --features ci,hermit/dhcpv4,hermit/tcp --netdev virtio-net-mmio
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --features ci,hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package testudp --features hermit/udp,hermit/dhcpv4 --netdev virtio-net-pci
-        if: matrix.arch != 'riscv64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package testudp --features hermit/udp,hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package miotcp --features hermit/dhcpv4 --netdev virtio-net-pci
-        if: matrix.arch != 'riscv64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package miotcp --features hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
-        if: matrix.arch == 'x86_64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package poll --features hermit/dhcpv4 --netdev virtio-net-pci
-        if: matrix.arch != 'riscv64'
-      - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package poll --features hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
-        if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package hello_world
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package wasmtime-demo --features ci
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package hello_world --no-default-features --microvm
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd --smp 4
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd --no-default-virtio-features
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --features fs --virtiofsd --no-default-virtio-features --smp 4
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rusty_demo --smp 4
+      #   # https://github.com/hermit-os/kernel/issues/737
+      #   if: matrix.arch != 'aarch64'
+      #   # https://github.com/hermit-os/kernel/issues/1286
+      #   continue-on-error: ${{ matrix.arch == 'riscv64' }}
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package rftrace-example --virtiofsd
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --features ci,hermit/dhcpv4 --netdev virtio-net-pci
+      #   if: matrix.arch != 'riscv64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --features ci,hermit/dhcpv4 --netdev virtio-net-pci --no-default-virtio-features
+      #   if: matrix.arch != 'riscv64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --no-default-features --microvm --features ci,hermit/dhcpv4,hermit/tcp --netdev virtio-net-mmio
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package httpd --features ci,hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package testudp --features hermit/udp,hermit/dhcpv4 --netdev virtio-net-pci
+      #   if: matrix.arch != 'riscv64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package testudp --features hermit/udp,hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package miotcp --features hermit/dhcpv4 --netdev virtio-net-pci
+      #   if: matrix.arch != 'riscv64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package miotcp --features hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
+      #   if: matrix.arch == 'x86_64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package poll --features hermit/dhcpv4 --netdev virtio-net-pci
+      #   if: matrix.arch != 'riscv64'
+      # - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package poll --features hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
+      #   if: matrix.arch == 'x86_64'
       - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package mioudp --features hermit/udp,hermit/dhcpv4 --netdev virtio-net-pci
         if: matrix.arch != 'riscv64'
       - run: cargo xtask ci qemu --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} ${{ matrix.flags }} --package mioudp --features hermit/udp,hermit/dhcpv4 --netdev rtl8139 --features hermit/rtl8139
         if: matrix.arch == 'x86_64'
-      - run: UHYVE=$CARGO_HOME/bin/uhyve cargo xtask ci uhyve --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --sudo --package rusty_demo
-        if: matrix.arch == 'x86_64'
-      - run: UHYVE=$CARGO_HOME/bin/uhyve cargo xtask ci uhyve --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --sudo --package rusty_demo --smp
-        if: matrix.arch == 'x86_64'
-      - run: FIRECRACKER=$HOME/.local/bin/firecracker cargo xtask ci firecracker --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --sudo --package hello_world --no-default-features
-        if: matrix.arch == 'x86_64'
+      # - run: UHYVE=$CARGO_HOME/bin/uhyve cargo xtask ci uhyve --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --sudo --package rusty_demo
+      #   if: matrix.arch == 'x86_64'
+      # - run: UHYVE=$CARGO_HOME/bin/uhyve cargo xtask ci uhyve --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --sudo --package rusty_demo --smp
+      #   if: matrix.arch == 'x86_64'
+      # - run: FIRECRACKER=$HOME/.local/bin/firecracker cargo xtask ci firecracker --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --sudo --package hello_world --no-default-features
+      #   if: matrix.arch == 'x86_64'
diff --git a/xtask/src/ci/qemu.rs b/xtask/src/ci/qemu.rs
index b33f88648d..0da56f0b47 100644
--- a/xtask/src/ci/qemu.rs
+++ b/xtask/src/ci/qemu.rs
@@ -380,14 +380,16 @@ fn test_mioudp() -> Result<()> {
 	thread::sleep(Duration::from_secs(10));
 	let buf = "exit";
 	eprintln!("[CI] send {buf:?} via UDP to 127.0.0.1:9975");
-	let socket = UdpSocket::bind("127.0.0.1:0")?;
-	socket.connect("127.0.0.1:9975")?;
-	socket.send(buf.as_bytes())?;
+	let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+	socket.connect("127.0.0.1:9975").unwrap();
+	socket.send(buf.as_bytes()).unwrap();
 
-	socket.set_read_timeout(Some(Duration::from_secs(10)))?;
+	socket
+		.set_read_timeout(Some(Duration::from_secs(10)))
+		.unwrap();
 	let mut buf = [0; 128];
-	let received = socket.recv(&mut buf)?;
-	eprintln!("[CI] receive: {}", from_utf8(&buf[..received])?);
+	let received = socket.recv(&mut buf).unwrap();
+	eprintln!("[CI] receive: {}", from_utf8(&buf[..received]).unwrap());
 
 	Ok(())
 }