RFC 9131 changes default behaviour of handling RX of NA messages when the corresponding entry is absent in the neighbour cache. The current implementation is limited to accept just unsolicited NAs. However, the RFC is more generic where it also accepts solicited NAs. Both types should result in adding a STALE entry for this case.

Expand accept_untracked_na behaviour to also accept solicited NAs to be compliant with the RFC and rename the sysctl knob to accept_untracked_na.

Fixes: f9a2fb73318e ("net/ipv6: Introduce accept_unsolicited_na knob to implement router-side changes for RFC9131") Signed-off-by: Arun Ajith S aajith@arista.com --- This change updates the accept_unsolicited_na feature that merged to net-next for v5.19 to be better compliant with the RFC. It also involves renaming the sysctl knob to accept_untracked_na before shipping in a release.

Note that the behaviour table has been modifed in the code comments, but dropped from the Documentation. This is because the table documents behaviour that is not unique to the knob, and it is more relevant to understanding the code. The documentation has been updated to be unambiguous even without the table.

v2: 1. Changed commit message and subject as suggested. 2. Added Fixes tag. 3. Used en-uk spellings consistently. 4. Added a couple of missing comments. 5. Refactored patch to be smaller by avoiding early return. 6. Made the documentation more clearer.

Documentation/networking/ip-sysctl.rst | 23 ++++------- include/linux/ipv6.h | 2 +- include/uapi/linux/ipv6.h | 2 +- net/ipv6/addrconf.c | 6 +-- net/ipv6/ndisc.c | 41 +++++++++++-------- .../net/ndisc_unsolicited_na_test.sh | 23 +++++------ 6 files changed, 49 insertions(+), 48 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index b882d4238581..04216564a03c 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -2474,21 +2474,16 @@ 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. +accept_untracked_na - BOOLEAN + Add a new neighbour cache entry in STALE state for routers on receiving a + neighbour advertisement (either solicited or unsolicited) with target + link-layer address option specified if no neighbour entry is already + present for the advertised IPv6 address. Without this knob, NAs received + for untracked addresses (absent in neighbour cache) are silently ignored. + + This is as per router-side behaviour documented in RFC9131.

- ==== ====== ====== ============================================== - 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 has lower precedence than drop_unsolicited_na.

This will optimize the return path for the initial off-link communication that is initiated by a directly connected host, by ensuring that diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h index 38c8203d52cb..37dfdcfcdd54 100644 --- a/include/linux/ipv6.h +++ b/include/linux/ipv6.h @@ -61,7 +61,7 @@ struct ipv6_devconf { __s32 suppress_frag_ndisc; __s32 accept_ra_mtu; __s32 drop_unsolicited_na; - __s32 accept_unsolicited_na; + __s32 accept_untracked_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 549ddeaf788b..03cdbe798fe3 100644 --- a/include/uapi/linux/ipv6.h +++ b/include/uapi/linux/ipv6.h @@ -194,7 +194,7 @@ enum { DEVCONF_IOAM6_ID, DEVCONF_IOAM6_ID_WIDE, DEVCONF_NDISC_EVICT_NOCARRIER, - DEVCONF_ACCEPT_UNSOLICITED_NA, + DEVCONF_ACCEPT_UNTRACKED_NA, DEVCONF_MAX };

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index ca0aa744593e..1b1932502e9e 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -5586,7 +5586,7 @@ 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; + array[DEVCONF_ACCEPT_UNTRACKED_NA] = cnf->accept_untracked_na; }

static inline size_t inet6_ifla6_size(void) @@ -7038,8 +7038,8 @@ static const struct ctl_table addrconf_sysctl[] = { .extra2 = (void *)SYSCTL_ONE, }, { - .procname = "accept_unsolicited_na", - .data = &ipv6_devconf.accept_unsolicited_na, + .procname = "accept_untracked_na", + .data = &ipv6_devconf.accept_untracked_na, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 254addad0dd3..ed0bbe87e345 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -979,7 +979,6 @@ 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"); @@ -1000,7 +999,7 @@ 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 + * drop_unsolicited_na takes precedence over accept_untracked_na */ if (!msg->icmph.icmp6_solicited && idev && idev->cnf.drop_unsolicited_na) @@ -1041,25 +1040,33 @@ 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. + * NAs with Target LL Address option without a corresponding + * entry in the neighbour cache can now create a STALE neighbour + * cache entry on routers. + * + * entry accept fwding solicited behaviour + * ------- ------ ------ --------- ---------------------- + * present X X 0 Set state to STALE + * present X X 1 Set state to REACHABLE + * absent 0 X X Do nothing + * absent 1 0 X Do nothing + * absent 1 1 X Add a new STALE entry * - * 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); + new_state = msg->icmph.icmp6_solicited ? NUD_REACHABLE : NUD_STALE; + if (!neigh && lladdr && + idev && idev->cnf.forwarding && + idev->cnf.accept_untracked_na) { + neigh = neigh_create(&nd_tbl, &msg->target, dev); + new_state = NUD_STALE; + }

- if (neigh) { + if (neigh && !IS_ERR(neigh)) { u8 old_flags = neigh->flags; struct net *net = dev_net(dev);

@@ -1079,7 +1086,7 @@ static void ndisc_recv_na(struct sk_buff *skb) }

ndisc_update(dev, neigh, lladdr, - msg->icmph.icmp6_solicited ? NUD_REACHABLE : NUD_STALE, + new_state, NEIGH_UPDATE_F_WEAK_OVERRIDE| (msg->icmph.icmp6_override ? NEIGH_UPDATE_F_OVERRIDE : 0)| NEIGH_UPDATE_F_OVERRIDE_ISROUTER| diff --git a/tools/testing/selftests/net/ndisc_unsolicited_na_test.sh b/tools/testing/selftests/net/ndisc_unsolicited_na_test.sh index f508657ee126..86e621b7b9c7 100755 --- a/tools/testing/selftests/net/ndisc_unsolicited_na_test.sh +++ b/tools/testing/selftests/net/ndisc_unsolicited_na_test.sh @@ -1,15 +1,14 @@ #!/bin/bash # SPDX-License-Identifier: GPL-2.0

-# This test is for the accept_unsolicited_na feature to +# This test is for the accept_untracked_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 +# 1 X X Don't update NC +# 0 0 X Don't update NC +# 0 1 0 Don't update NC +# 0 1 1 Add a STALE NC entry

ret=0 # Kselftest framework requirement - SKIP code is 4. @@ -72,7 +71,7 @@ setup() set -e

local drop_unsolicited_na=$1 - local accept_unsolicited_na=$2 + local accept_untracked_na=$2 local forwarding=$3

# Setup two namespaces and a veth tunnel across them. @@ -93,7 +92,7 @@ setup() ${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} + ${ROUTER_CONF}.accept_untracked_na=${accept_untracked_na} ${IP_ROUTER_EXEC} sysctl -qw ${ROUTER_CONF}.disable_ipv6=0 ${IP_ROUTER} addr add ${ROUTER_ADDR_WITH_MASK} dev ${ROUTER_INTF}

@@ -144,13 +143,13 @@ link_up() {

verify_ndisc() { local drop_unsolicited_na=$1 - local accept_unsolicited_na=$2 + local accept_untracked_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 ] && \ + [ ${accept_untracked_na} -eq 1 ] && \ [ ${forwarding} -eq 1 ]; then # Neighbour entry expected to be present for 011 case [[ ${neigh_show_output} ]] @@ -179,14 +178,14 @@ test_unsolicited_na_combination() { test_unsolicited_na_common $1 $2 $3 test_msg=("test_unsolicited_na: " "drop_unsolicited_na=$1 " - "accept_unsolicited_na=$2 " + "accept_untracked_na=$2 " "forwarding=$3") log_test $? 0 "${test_msg[*]}" cleanup }

test_unsolicited_na_combinations() { - # Args: drop_unsolicited_na accept_unsolicited_na forwarding + # Args: drop_unsolicited_na accept_untracked_na forwarding

# Expect entry test_unsolicited_na_combination 0 1 1