Add a new neighbour cache entry in STALE state for routers on receiving
an unsolicited (gratuitous) neighbour advertisement with
target link-layer-address option specified.
This is similar to the arp_accept configuration for IPv4.
A new sysctl endpoint is created to turn on this behaviour:
/proc/sys/net/ipv6/conf/interface/accept_unsolicited_na.
Signed-off-by: Arun Ajith S <aajith@xxxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
---
Documentation/networking/ip-sysctl.rst | 23 ++
include/linux/ipv6.h | 1 +
include/uapi/linux/ipv6.h | 1 +
net/ipv6/addrconf.c | 10 +
net/ipv6/ndisc.c | 20 +-
tools/testing/selftests/net/Makefile | 1 +
.../net/ndisc_unsolicited_na_test.sh | 255 ++++++++++++++++++
7 files changed, 310 insertions(+), 1 deletion(-)
create mode 100755 tools/testing/selftests/net/ndisc_unsolicited_na_test.sh
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index b0024aa7b051..9e17efe343ac 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -2467,6 +2467,29 @@ drop_unsolicited_na - BOOLEAN
By default this is turned off.
+accept_unsolicited_na - BOOLEAN
+ Add a new neighbour cache entry in STALE state for routers on receiving an
+ unsolicited neighbour advertisement with target link-layer address option
+ specified. This is as per router-side behavior documented in RFC9131.
+ This has lower precedence than drop_unsolicited_na.
+ drop accept fwding behaviour
+ ---- ------ ------ ----------------------------------------------
+ 1 X X Drop NA packet and don't pass up the stack
+ 0 0 X Pass NA packet up the stack, don't update NC
+ 0 1 0 Pass NA packet up the stack, don't update NC
+ 0 1 1 Pass NA packet up the stack, and add a STALE
+ NC entry
+ This will optimize the return path for the initial off-link communication
+ that is initiated by a directly connected host, by ensuring that
+ the first-hop router which turns on this setting doesn't have to
+ buffer the initial return packets to do neighbour-solicitation.
+ The prerequisite is that the host is configured to send
+ unsolicited neighbour advertisements on interface bringup.
+ This setting should be used in conjunction with the ndisc_notify setting
+ on the host to satisfy this prerequisite.
+
+ By default this is turned off.
+
enhanced_dad - BOOLEAN
Include a nonce option in the IPv6 neighbor solicitation messages used for
duplicate address detection per RFC7527. A received DAD NS will only signal
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 16870f86c74d..918bfea4ef5f 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -61,6 +61,7 @@ struct ipv6_devconf {
__s32 suppress_frag_ndisc;
__s32 accept_ra_mtu;
__s32 drop_unsolicited_na;
+ __s32 accept_unsolicited_na;
struct ipv6_stable_secret {
bool initialized;
struct in6_addr secret;
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index d4178dace0bf..549ddeaf788b 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -194,6 +194,7 @@ enum {
DEVCONF_IOAM6_ID,
DEVCONF_IOAM6_ID_WIDE,
DEVCONF_NDISC_EVICT_NOCARRIER,
+ DEVCONF_ACCEPT_UNSOLICITED_NA,
DEVCONF_MAX
};
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 1afc4c024981..6473dc84b71d 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5587,6 +5587,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
array[DEVCONF_IOAM6_ID] = cnf->ioam6_id;
array[DEVCONF_IOAM6_ID_WIDE] = cnf->ioam6_id_wide;
array[DEVCONF_NDISC_EVICT_NOCARRIER] = cnf->ndisc_evict_nocarrier;
+ array[DEVCONF_ACCEPT_UNSOLICITED_NA] = cnf->accept_unsolicited_na;
}
static inline size_t inet6_ifla6_size(void)
@@ -7037,6 +7038,15 @@ static const struct ctl_table addrconf_sysctl[] = {
.extra1 = (void *)SYSCTL_ZERO,
.extra2 = (void *)SYSCTL_ONE,
},
+ {
+ .procname = "accept_unsolicited_na",
+ .data = &ipv6_devconf.accept_unsolicited_na,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = (void *)SYSCTL_ZERO,
+ .extra2 = (void *)SYSCTL_ONE,
+ },
{
/* sentinel */
}
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index fcb288b0ae13..254addad0dd3 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -979,6 +979,7 @@ static void ndisc_recv_na(struct sk_buff *skb)
struct inet6_dev *idev = __in6_dev_get(dev);
struct inet6_ifaddr *ifp;
struct neighbour *neigh;
+ bool create_neigh;
if (skb->len < sizeof(struct nd_msg)) {
ND_PRINTK(2, warn, "NA: packet too short\n");
@@ -999,6 +1000,7 @@ static void ndisc_recv_na(struct sk_buff *skb)
/* For some 802.11 wireless deployments (and possibly other networks),
* there will be a NA proxy and unsolicitd packets are attacks
* and thus should not be accepted.
+ * drop_unsolicited_na takes precedence over accept_unsolicited_na
*/
if (!msg->icmph.icmp6_solicited && idev &&
idev->cnf.drop_unsolicited_na)
@@ -1039,7 +1041,23 @@ static void ndisc_recv_na(struct sk_buff *skb)
in6_ifa_put(ifp);
return;
}
- neigh = neigh_lookup(&nd_tbl, &msg->target, dev);
+ /* RFC 9131 updates original Neighbour Discovery RFC 4861.
+ * An unsolicited NA can now create a neighbour cache entry
+ * on routers if it has Target LL Address option.
+ *
+ * drop accept fwding behaviour
+ * ---- ------ ------ ----------------------------------------------
+ * 1 X X Drop NA packet and don't pass up the stack
+ * 0 0 X Pass NA packet up the stack, don't update NC
+ * 0 1 0 Pass NA packet up the stack, don't update NC
+ * 0 1 1 Pass NA packet up the stack, and add a STALE
+ * NC entry
+ * Note that we don't do a (daddr == all-routers-mcast) check.
+ */
+ create_neigh = !msg->icmph.icmp6_solicited && lladdr &&
+ idev && idev->cnf.forwarding &&
+ idev->cnf.accept_unsolicited_na;
+ neigh = __neigh_lookup(&nd_tbl, &msg->target, dev, create_neigh);
if (neigh) {
u8 old_flags = neigh->flags;
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 3fe2515aa616..af7f6e6ff182 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -36,6 +36,7 @@ TEST_PROGS += srv6_end_dt4_l3vpn_test.sh
TEST_PROGS += srv6_end_dt6_l3vpn_test.sh
TEST_PROGS += vrf_strict_mode_test.sh
TEST_PROGS += arp_ndisc_evict_nocarrier.sh
+TEST_PROGS += ndisc_unsolicited_na_test.sh
TEST_PROGS_EXTENDED := in_netns.sh setup_loopback.sh setup_veth.sh
TEST_PROGS_EXTENDED += toeplitz_client.sh toeplitz.sh
TEST_GEN_FILES = socket nettest
diff --git a/tools/testing/selftests/net/ndisc_unsolicited_na_test.sh b/tools/testing/selftests/net/ndisc_unsolicited_na_test.sh
new file mode 100755
index 000000000000..f508657ee126
--- /dev/null
+++ b/tools/testing/selftests/net/ndisc_unsolicited_na_test.sh
@@ -0,0 +1,255 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# This test is for the accept_unsolicited_na feature to
+# enable RFC9131 behaviour. The following is the test-matrix.
+# drop accept fwding behaviour
+# ---- ------ ------ ----------------------------------------------
+# 1 X X Drop NA packet and don't pass up the stack
+# 0 0 X Pass NA packet up the stack, don't update NC
+# 0 1 0 Pass NA packet up the stack, don't update NC
+# 0 1 1 Pass NA packet up the stack, and add a STALE
+# NC entry
+
+ret=0
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+PAUSE_ON_FAIL=no
+PAUSE=no
+
+HOST_NS="ns-host"
+ROUTER_NS="ns-router"
+
+HOST_INTF="veth-host"
+ROUTER_INTF="veth-router"
+
+ROUTER_ADDR="2000:20::1"
+HOST_ADDR="2000:20::2"
+SUBNET_WIDTH=64
+ROUTER_ADDR_WITH_MASK="${ROUTER_ADDR}/${SUBNET_WIDTH}"
+HOST_ADDR_WITH_MASK="${HOST_ADDR}/${SUBNET_WIDTH}"
+
+IP_HOST="ip -6 -netns ${HOST_NS}"
+IP_HOST_EXEC="ip netns exec ${HOST_NS}"
+IP_ROUTER="ip -6 -netns ${ROUTER_NS}"
+IP_ROUTER_EXEC="ip netns exec ${ROUTER_NS}"
+
+tcpdump_stdout=
+tcpdump_stderr=
+
+log_test()
+{
+ local rc=$1
+ local expected=$2
+ local msg="$3"
+
+ if [ ${rc} -eq ${expected} ]; then
+ printf " TEST: %-60s [ OK ]\n" "${msg}"
+ nsuccess=$((nsuccess+1))
+ else
+ ret=1
+ nfail=$((nfail+1))
+ printf " TEST: %-60s [FAIL]\n" "${msg}"
+ if [ "${PAUSE_ON_FAIL}" = "yes" ]; then
+ echo
+ echo "hit enter to continue, 'q' to quit"
+ read a
+ [ "$a" = "q" ] && exit 1
+ fi
+ fi
+
+ if [ "${PAUSE}" = "yes" ]; then
+ echo
+ echo "hit enter to continue, 'q' to quit"
+ read a
+ [ "$a" = "q" ] && exit 1
+ fi
+}
+
+setup()
+{
+ set -e
+
+ local drop_unsolicited_na=$1
+ local accept_unsolicited_na=$2
+ local forwarding=$3
+
+ # Setup two namespaces and a veth tunnel across them.
+ # On end of the tunnel is a router and the other end is a host.
+ ip netns add ${HOST_NS}
+ ip netns add ${ROUTER_NS}
+ ${IP_ROUTER} link add ${ROUTER_INTF} type veth \
+ peer name ${HOST_INTF} netns ${HOST_NS}
+
+ # Enable IPv6 on both router and host, and configure static addresses.
+ # The router here is the DUT
+ # Setup router configuration as specified by the arguments.
+ # forwarding=0 case is to check that a non-router
+ # doesn't add neighbour entries.
+ ROUTER_CONF=net.ipv6.conf.${ROUTER_INTF}
+ ${IP_ROUTER_EXEC} sysctl -qw \
+ ${ROUTER_CONF}.forwarding=${forwarding}
+ ${IP_ROUTER_EXEC} sysctl -qw \
+ ${ROUTER_CONF}.drop_unsolicited_na=${drop_unsolicited_na}
+ ${IP_ROUTER_EXEC} sysctl -qw \
+ ${ROUTER_CONF}.accept_unsolicited_na=${accept_unsolicited_na}
+ ${IP_ROUTER_EXEC} sysctl -qw ${ROUTER_CONF}.disable_ipv6=0
+ ${IP_ROUTER} addr add ${ROUTER_ADDR_WITH_MASK} dev ${ROUTER_INTF}
+
+ # Turn on ndisc_notify on host interface so that
+ # the host sends unsolicited NAs.
+ HOST_CONF=net.ipv6.conf.${HOST_INTF}
+ ${IP_HOST_EXEC} sysctl -qw ${HOST_CONF}.ndisc_notify=1
+ ${IP_HOST_EXEC} sysctl -qw ${HOST_CONF}.disable_ipv6=0
+ ${IP_HOST} addr add ${HOST_ADDR_WITH_MASK} dev ${HOST_INTF}
+
+ set +e
+}
+
+start_tcpdump() {
+ set -e
+ tcpdump_stdout=`mktemp`
+ tcpdump_stderr=`mktemp`
+ ${IP_ROUTER_EXEC} timeout 15s \
+ tcpdump --immediate-mode -tpni ${ROUTER_INTF} -c 1 \
+ "icmp6 && icmp6[0] == 136 && src ${HOST_ADDR}" \
+ > ${tcpdump_stdout} 2> /dev/null
+ set +e
+}
+
+cleanup_tcpdump()
+{
+ set -e
+ [[ ! -z ${tcpdump_stdout} ]] && rm -f ${tcpdump_stdout}
+ [[ ! -z ${tcpdump_stderr} ]] && rm -f ${tcpdump_stderr}
+ tcpdump_stdout=
+ tcpdump_stderr=
+ set +e
+}
+
+cleanup()
+{
+ cleanup_tcpdump
+ ip netns del ${HOST_NS}
+ ip netns del ${ROUTER_NS}
+}
+
+link_up() {
+ set -e
+ ${IP_ROUTER} link set dev ${ROUTER_INTF} up
+ ${IP_HOST} link set dev ${HOST_INTF} up
+ set +e
+}
+
+verify_ndisc() {
+ local drop_unsolicited_na=$1
+ local accept_unsolicited_na=$2
+ local forwarding=$3
+
+ neigh_show_output=$(${IP_ROUTER} neigh show \
+ to ${HOST_ADDR} dev ${ROUTER_INTF} nud stale)
+ if [ ${drop_unsolicited_na} -eq 0 ] && \
+ [ ${accept_unsolicited_na} -eq 1 ] && \
+ [ ${forwarding} -eq 1 ]; then
+ # Neighbour entry expected to be present for 011 case
+ [[ ${neigh_show_output} ]]
+ else
+ # Neighbour entry expected to be absent for all other cases
+ [[ -z ${neigh_show_output} ]]
+ fi
+}
+
+test_unsolicited_na_common()
+{
+ # Setup the test bed, but keep links down
+ setup $1 $2 $3
+
+ # Bring the link up, wait for the NA,
+ # and add a delay to ensure neighbour processing is done.
+ link_up
+ start_tcpdump
+
+ # Verify the neighbour table
+ verify_ndisc $1 $2 $3
+
+}
+
+test_unsolicited_na_combination() {
+ test_unsolicited_na_common $1 $2 $3
+ test_msg=("test_unsolicited_na: "
+ "drop_unsolicited_na=$1 "
+ "accept_unsolicited_na=$2 "
+ "forwarding=$3")
+ log_test $? 0 "${test_msg[*]}"
+ cleanup
+}
+
+test_unsolicited_na_combinations() {
+ # Args: drop_unsolicited_na accept_unsolicited_na forwarding
+
+ # Expect entry
+ test_unsolicited_na_combination 0 1 1
+
+ # Expect no entry
+ test_unsolicited_na_combination 0 0 0
+ test_unsolicited_na_combination 0 0 1
+ test_unsolicited_na_combination 0 1 0
+ test_unsolicited_na_combination 1 0 0
+ test_unsolicited_na_combination 1 0 1
+ test_unsolicited_na_combination 1 1 0
+ test_unsolicited_na_combination 1 1 1
+}
+
+###############################################################################
+# usage
+
+usage()
+{
+ cat <<EOF
+usage: ${0##*/} OPTS
+ -p Pause on fail
+ -P Pause after each test before cleanup
+EOF
+}
+
+###############################################################################
+# main
+
+while getopts :pPh o
+do
+ case $o in
+ p) PAUSE_ON_FAIL=yes;;
+ P) PAUSE=yes;;
+ h) usage; exit 0;;
+ *) usage; exit 1;;
+ esac
+done
+
+# make sure we don't pause twice
+[ "${PAUSE}" = "yes" ] && PAUSE_ON_FAIL=no
+
+if [ "$(id -u)" -ne 0 ];then
+ echo "SKIP: Need root privileges"
+ exit $ksft_skip;
+fi
+
+if [ ! -x "$(command -v ip)" ]; then
+ echo "SKIP: Could not run test without ip tool"
+ exit $ksft_skip
+fi
+
+if [ ! -x "$(command -v tcpdump)" ]; then
+ echo "SKIP: Could not run test without tcpdump tool"
+ exit $ksft_skip
+fi
+
+# start clean
+cleanup &> /dev/null
+
+test_unsolicited_na_combinations
+
+printf "\nTests passed: %3d\n" ${nsuccess}
+printf "Tests failed: %3d\n" ${nfail}
+
+exit $ret
--
2.27.0
---
Changes from v3:
1. Fix typo in new test file extension: .py -> .sh
2. Add Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Note that I am keeping the knob as a sysctl for consistency with existing ND and ARP knobs as suggested by David.
