Merge branch 'netpoll-factor-out-functions-from-netpoll_send_udp-and-add-ipv6-selftest'

Breno Leitao says:

====================
netpoll: Factor out functions from netpoll_send_udp() and add ipv6 selftest

Refactors the netpoll UDP transmit path to improve code clarity,
maintainability, and protocol-layer encapsulation.

Function netpoll_send_udp() has more than 100 LoC, which is hard to
understand and review. After this patchset, it has only 32 LoC, which is
more manageable.

The series systematically moves the construction of protocol headers
(UDP, IPv4, IPv6, Ethernet) out of the core `netpoll_send_udp()`
function into dedicated static helpers:

  - `push_udp()` for UDP header setup
  - `push_ipv4()` and `push_ipv6()` for IP header setup
  - `push_eth()` for Ethernet header setup

This results in a clean, layered abstraction that mirrors the protocol
stack, reduces code duplication, and improves readability.

Also, to make sure this is not breaking anything, add IPv6 selftest to
netconsole tests, which will exercise this code. This test would also pick
problems similiar to the one fixed by f599020702698  ("net: netpoll:
Initialize UDP checksum field before checksumming"), which was
embarrassin we didn't have a selftest catch it.

Anyway, there are **no functional changes** intended in this patchset.

v1: https://lore.kernel.org/20250627-netpoll_untagle_ip-v1-0-61a21692f84a@debian.org
====================

Link: https://patch.msgid.link/20250702-netpoll_untagle_ip-v2-0-13cf3db24e2b@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 99 insertions, 30 deletions

diff --git a/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh b/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh
index 3fcf85a34596..258af805497b 100644
--- a/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh
+++ b/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh
@@ -11,9 +11,11 @@ set -euo pipefail
 LIBDIR=$(dirname "$(readlink -e "${BASH_SOURCE[0]}")")
 
 SRCIF="" # to be populated later
-SRCIP=192.0.2.1
+SRCIP4="192.0.2.1"
+SRCIP6="fc00::1"
 DSTIF="" # to be populated later
-DSTIP=192.0.2.2
+DSTIP4="192.0.2.2"
+DSTIP6="fc00::2"
 
 PORT="6666"
 MSG="netconsole selftest"
@@ -80,7 +82,23 @@ function configure_ip() {
 	ip link set "${SRCIF}" up
 }
 
+function select_ipv4_or_ipv6()
+{
+	local VERSION=${1}
+
+	if [[ "$VERSION" == "ipv6" ]]
+	then
+		DSTIP="${DSTIP6}"
+		SRCIP="${SRCIP6}"
+	else
+		DSTIP="${DSTIP4}"
+		SRCIP="${SRCIP4}"
+	fi
+}
+
 function set_network() {
+	local IP_VERSION=${1:-"ipv4"}
+
 	# setup_ns function is coming from lib.sh
 	setup_ns NAMESPACE
 
@@ -91,6 +109,7 @@ function set_network() {
 	# Link both interfaces back to back
 	link_ifaces
 
+	select_ipv4_or_ipv6 "${IP_VERSION}"
 	configure_ip
 }
 
@@ -119,6 +138,11 @@ function create_dynamic_target() {
 	fi
 
 	echo 1 > "${NETCONS_PATH}"/enabled
+
+	# This will make sure that the kernel was able to
+	# load the netconsole driver configuration. The console message
+	# gets more organized/sequential as well.
+	sleep 1
 }
 
 # Generate the command line argument for netconsole following:
@@ -179,9 +203,18 @@ function set_user_data() {
 
 function listen_port_and_save_to() {
 	local OUTPUT=${1}
+	local IPVERSION=${2:-"ipv4"}
+
+	if [ "${IPVERSION}" == "ipv4" ]
+	then
+		SOCAT_MODE="UDP-LISTEN"
+	else
+		SOCAT_MODE="UDP6-LISTEN"
+	fi
+
 	# Just wait for 2 seconds
 	timeout 2 ip netns exec "${NAMESPACE}" \
-		socat UDP-LISTEN:"${PORT}",fork "${OUTPUT}"
+		socat "${SOCAT_MODE}":"${PORT}",fork "${OUTPUT}"
 }
 
 # Only validate that the message arrived properly
@@ -263,8 +296,15 @@ function check_for_dependencies() {
 		exit "${ksft_skip}"
 	fi
 
-	if ip addr list | grep -E "inet.*(${SRCIP}|${DSTIP})" 2> /dev/null; then
-		echo "SKIP: IPs already in use. Skipping it" >&2
+	REGEXP4="inet.*(${SRCIP4}|${DSTIP4})"
+	REGEXP6="inet.*(${SRCIP6}|${DSTIP6})"
+	if ip addr list | grep -E "${REGEXP4}" 2> /dev/null; then
+		echo "SKIP: IPv4s already in use. Skipping it" >&2
+		exit "${ksft_skip}"
+	fi
+
+	if ip addr list | grep -E "${REGEXP6}" 2> /dev/null; then
+		echo "SKIP: IPv6s already in use. Skipping it" >&2
 		exit "${ksft_skip}"
 	fi
 }
@@ -278,11 +318,13 @@ function check_for_taskset() {
 
 # This is necessary if running multiple tests in a row
 function pkill_socat() {
-	PROCESS_NAME="socat UDP-LISTEN:6666,fork ${OUTPUT_FILE}"
+	PROCESS_NAME4="socat UDP-LISTEN:6666,fork ${OUTPUT_FILE}"
+	PROCESS_NAME6="socat UDP6-LISTEN:6666,fork ${OUTPUT_FILE}"
 	# socat runs under timeout(1), kill it if it is still alive
 	# do not fail if socat doesn't exist anymore
 	set +e
-	pkill -f "${PROCESS_NAME}"
+	pkill -f "${PROCESS_NAME4}"
+	pkill -f "${PROCESS_NAME6}"
 	set -e
 }
 
@@ -294,3 +336,23 @@ function check_netconsole_module() {
 		exit "${ksft_skip}"
 	fi
 }
+
+# A wrapper to translate protocol version to udp version
+function wait_for_port() {
+	local NAMESPACE=${1}
+	local PORT=${2}
+	IP_VERSION=${3}
+
+	if [ "${IP_VERSION}" == "ipv6" ]
+	then
+		PROTOCOL="udp6"
+	else
+		PROTOCOL="udp"
+	fi
+
+	wait_local_port_listen "${NAMESPACE}" "${PORT}" "${PROTOCOL}"
+	# even after the port is open, let's wait 1 second before writing
+	# otherwise the packet could be missed, and the test will fail. Happens
+	# more frequently on IPv6
+	sleep 1
+}
diff --git a/tools/testing/selftests/drivers/net/netcons_basic.sh b/tools/testing/selftests/drivers/net/netcons_basic.sh
index 40a6ac6191b8..a3446b569976 100755
--- a/tools/testing/selftests/drivers/net/netcons_basic.sh
+++ b/tools/testing/selftests/drivers/net/netcons_basic.sh
@@ -36,30 +36,37 @@ trap cleanup EXIT
 # Run the test twice, with different format modes
 for FORMAT in "basic" "extended"
 do
-	echo "Running with target mode: ${FORMAT}"
-	# Create one namespace and two interfaces
-	set_network
-	# Create a dynamic target for netconsole
-	create_dynamic_target "${FORMAT}"
-	# Only set userdata for extended format
-	if [ "$FORMAT" == "extended" ]
-	then
-		# Set userdata "key" with the "value" value
-		set_user_data
-	fi
-	# Listed for netconsole port inside the namespace and destination interface
-	listen_port_and_save_to "${OUTPUT_FILE}" &
-	# Wait for socat to start and listen to the port.
-	wait_local_port_listen "${NAMESPACE}" "${PORT}" udp
-	# Send the message
-	echo "${MSG}: ${TARGET}" > /dev/kmsg
-	# Wait until socat saves the file to disk
-	busywait "${BUSYWAIT_TIMEOUT}" test -s "${OUTPUT_FILE}"
+	for IP_VERSION in "ipv6" "ipv4"
+	do
+		echo "Running with target mode: ${FORMAT} (${IP_VERSION})"
+		# Create one namespace and two interfaces
+		set_network "${IP_VERSION}"
+		# Create a dynamic target for netconsole
+		create_dynamic_target "${FORMAT}"
+		# Only set userdata for extended format
+		if [ "$FORMAT" == "extended" ]
+		then
+			# Set userdata "key" with the "value" value
+			set_user_data
+		fi
+		# Listed for netconsole port inside the namespace and
+		# destination interface
+		listen_port_and_save_to "${OUTPUT_FILE}" "${IP_VERSION}" &
+		# Wait for socat to start and listen to the port.
+		wait_for_port "${NAMESPACE}" "${PORT}" "${IP_VERSION}"
+		# Send the message
+		echo "${MSG}: ${TARGET}" > /dev/kmsg
+		# Wait until socat saves the file to disk
+		busywait "${BUSYWAIT_TIMEOUT}" test -s "${OUTPUT_FILE}"
 
-	# Make sure the message was received in the dst part
-	# and exit
-	validate_result "${OUTPUT_FILE}" "${FORMAT}"
-	cleanup
+		# Make sure the message was received in the dst part
+		# and exit
+		validate_result "${OUTPUT_FILE}" "${FORMAT}"
+		# kill socat in case it is still running
+		pkill_socat
+		cleanup
+		echo "${FORMAT} : ${IP_VERSION} : Test passed" >&2
+	done
 done
 
 trap - EXIT