From 183185a18ff96751db52a46ccf93fff3a1f42815 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 7 Mar 2025 20:28:53 +0100 Subject: [PATCH 1/2] gre: Fix IPv6 link-local address generation. Use addrconf_addr_gen() to generate IPv6 link-local addresses on GRE devices in most cases and fall back to using add_v4_addrs() only in case the GRE configuration is incompatible with addrconf_addr_gen(). GRE used to use addrconf_addr_gen() until commit e5dd729460ca ("ip/ip6_gre: use the same logic as SIT interfaces when computing v6LL address") restricted this use to gretap and ip6gretap devices, and created add_v4_addrs() (borrowed from SIT) for non-Ethernet GRE ones. The original problem came when commit 9af28511be10 ("addrconf: refuse isatap eui64 for INADDR_ANY") made __ipv6_isatap_ifid() fail when its addr parameter was 0. The commit says that this would create an invalid address, however, I couldn't find any RFC saying that the generated interface identifier would be wrong. Anyway, since gre over IPv4 devices pass their local tunnel address to __ipv6_isatap_ifid(), that commit broke their IPv6 link-local address generation when the local address was unspecified. Then commit e5dd729460ca ("ip/ip6_gre: use the same logic as SIT interfaces when computing v6LL address") tried to fix that case by defining add_v4_addrs() and calling it to generate the IPv6 link-local address instead of using addrconf_addr_gen() (apart for gretap and ip6gretap devices, which would still use the regular addrconf_addr_gen(), since they have a MAC address). That broke several use cases because add_v4_addrs() isn't properly integrated into the rest of IPv6 Neighbor Discovery code. Several of these shortcomings have been fixed over time, but add_v4_addrs() remains broken on several aspects. In particular, it doesn't send any Router Sollicitations, so the SLAAC process doesn't start until the interface receives a Router Advertisement. Also, add_v4_addrs() mostly ignores the address generation mode of the interface (/proc/sys/net/ipv6/conf/*/addr_gen_mode), thus breaking the IN6_ADDR_GEN_MODE_RANDOM and IN6_ADDR_GEN_MODE_STABLE_PRIVACY cases. Fix the situation by using add_v4_addrs() only in the specific scenario where the normal method would fail. That is, for interfaces that have all of the following characteristics: * run over IPv4, * transport IP packets directly, not Ethernet (that is, not gretap interfaces), * tunnel endpoint is INADDR_ANY (that is, 0), * device address generation mode is EUI64. In all other cases, revert back to the regular addrconf_addr_gen(). Also, remove the special case for ip6gre interfaces in add_v4_addrs(), since ip6gre devices now always use addrconf_addr_gen() instead. Fixes: e5dd729460ca ("ip/ip6_gre: use the same logic as SIT interfaces when computing v6LL address") Signed-off-by: Guillaume Nault Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/559c32ce5c9976b269e6337ac9abb6a96abe5096.1741375285.git.gnault@redhat.com Signed-off-by: Paolo Abeni --- net/ipv6/addrconf.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index ac8cc1076536..8b6258819dad 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -3209,16 +3209,13 @@ static void add_v4_addrs(struct inet6_dev *idev) struct in6_addr addr; struct net_device *dev; struct net *net = dev_net(idev->dev); - int scope, plen, offset = 0; + int scope, plen; u32 pflags = 0; ASSERT_RTNL(); memset(&addr, 0, sizeof(struct in6_addr)); - /* in case of IP6GRE the dev_addr is an IPv6 and therefore we use only the last 4 bytes */ - if (idev->dev->addr_len == sizeof(struct in6_addr)) - offset = sizeof(struct in6_addr) - 4; - memcpy(&addr.s6_addr32[3], idev->dev->dev_addr + offset, 4); + memcpy(&addr.s6_addr32[3], idev->dev->dev_addr, 4); if (!(idev->dev->flags & IFF_POINTOPOINT) && idev->dev->type == ARPHRD_SIT) { scope = IPV6_ADDR_COMPATv4; @@ -3529,7 +3526,13 @@ static void addrconf_gre_config(struct net_device *dev) return; } - if (dev->type == ARPHRD_ETHER) { + /* Generate the IPv6 link-local address using addrconf_addr_gen(), + * unless we have an IPv4 GRE device not bound to an IP address and + * which is in EUI64 mode (as __ipv6_isatap_ifid() would fail in this + * case). Such devices fall back to add_v4_addrs() instead. + */ + if (!(dev->type == ARPHRD_IPGRE && *(__be32 *)dev->dev_addr == 0 && + idev->cnf.addr_gen_mode == IN6_ADDR_GEN_MODE_EUI64)) { addrconf_addr_gen(idev, true); return; } From 6f50175ccad4278ed3a9394c00b797b75441bd6e Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 7 Mar 2025 20:28:58 +0100 Subject: [PATCH 2/2] selftests: Add IPv6 link-local address generation tests for GRE devices. GRE devices have their special code for IPv6 link-local address generation that has been the source of several regressions in the past. Add selftest to check that all gre, ip6gre, gretap and ip6gretap get an IPv6 link-link local address in accordance with the net.ipv6.conf..addr_gen_mode sysctl. Signed-off-by: Guillaume Nault Reviewed-by: Ido Schimmel Tested-by: Ido Schimmel Reviewed-by: Petr Machata Link: https://patch.msgid.link/2d6772af8e1da9016b2180ec3f8d9ee99f470c77.1741375285.git.gnault@redhat.com Signed-off-by: Paolo Abeni --- tools/testing/selftests/net/Makefile | 1 + .../testing/selftests/net/gre_ipv6_lladdr.sh | 177 ++++++++++++++++++ 2 files changed, 178 insertions(+) create mode 100755 tools/testing/selftests/net/gre_ipv6_lladdr.sh diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile index 73ee88d6b043..5916f3b81c39 100644 --- a/tools/testing/selftests/net/Makefile +++ b/tools/testing/selftests/net/Makefile @@ -31,6 +31,7 @@ TEST_PROGS += veth.sh TEST_PROGS += ioam6.sh TEST_PROGS += gro.sh TEST_PROGS += gre_gso.sh +TEST_PROGS += gre_ipv6_lladdr.sh TEST_PROGS += cmsg_so_mark.sh TEST_PROGS += cmsg_so_priority.sh TEST_PROGS += cmsg_time.sh cmsg_ipv6.sh diff --git a/tools/testing/selftests/net/gre_ipv6_lladdr.sh b/tools/testing/selftests/net/gre_ipv6_lladdr.sh new file mode 100755 index 000000000000..5b34f6e1f831 --- /dev/null +++ b/tools/testing/selftests/net/gre_ipv6_lladdr.sh @@ -0,0 +1,177 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 + +source ./lib.sh + +PAUSE_ON_FAIL="no" + +# The trap function handler +# +exit_cleanup_all() +{ + cleanup_all_ns + + exit "${EXIT_STATUS}" +} + +# Add fake IPv4 and IPv6 networks on the loopback device, to be used as +# underlay by future GRE devices. +# +setup_basenet() +{ + ip -netns "${NS0}" link set dev lo up + ip -netns "${NS0}" address add dev lo 192.0.2.10/24 + ip -netns "${NS0}" address add dev lo 2001:db8::10/64 nodad +} + +# Check if network device has an IPv6 link-local address assigned. +# +# Parameters: +# +# * $1: The network device to test +# * $2: An extra regular expression that should be matched (to verify the +# presence of extra attributes) +# * $3: The expected return code from grep (to allow checking the absence of +# a link-local address) +# * $4: The user visible name for the scenario being tested +# +check_ipv6_ll_addr() +{ + local DEV="$1" + local EXTRA_MATCH="$2" + local XRET="$3" + local MSG="$4" + + RET=0 + set +e + ip -netns "${NS0}" -6 address show dev "${DEV}" scope link | grep "fe80::" | grep -q "${EXTRA_MATCH}" + check_err_fail "${XRET}" $? "" + log_test "${MSG}" + set -e +} + +# Create a GRE device and verify that it gets an IPv6 link-local address as +# expected. +# +# Parameters: +# +# * $1: The device type (gre, ip6gre, gretap or ip6gretap) +# * $2: The local underlay IP address (can be an IPv4, an IPv6 or "any") +# * $3: The remote underlay IP address (can be an IPv4, an IPv6 or "any") +# * $4: The IPv6 interface identifier generation mode to use for the GRE +# device (eui64, none, stable-privacy or random). +# +test_gre_device() +{ + local GRE_TYPE="$1" + local LOCAL_IP="$2" + local REMOTE_IP="$3" + local MODE="$4" + local ADDR_GEN_MODE + local MATCH_REGEXP + local MSG + + ip link add netns "${NS0}" name gretest type "${GRE_TYPE}" local "${LOCAL_IP}" remote "${REMOTE_IP}" + + case "${MODE}" in + "eui64") + ADDR_GEN_MODE=0 + MATCH_REGEXP="" + MSG="${GRE_TYPE}, mode: 0 (EUI64), ${LOCAL_IP} -> ${REMOTE_IP}" + XRET=0 + ;; + "none") + ADDR_GEN_MODE=1 + MATCH_REGEXP="" + MSG="${GRE_TYPE}, mode: 1 (none), ${LOCAL_IP} -> ${REMOTE_IP}" + XRET=1 # No link-local address should be generated + ;; + "stable-privacy") + ADDR_GEN_MODE=2 + MATCH_REGEXP="stable-privacy" + MSG="${GRE_TYPE}, mode: 2 (stable privacy), ${LOCAL_IP} -> ${REMOTE_IP}" + XRET=0 + # Initialise stable_secret (required for stable-privacy mode) + ip netns exec "${NS0}" sysctl -qw net.ipv6.conf.gretest.stable_secret="2001:db8::abcd" + ;; + "random") + ADDR_GEN_MODE=3 + MATCH_REGEXP="stable-privacy" + MSG="${GRE_TYPE}, mode: 3 (random), ${LOCAL_IP} -> ${REMOTE_IP}" + XRET=0 + ;; + esac + + # Check that IPv6 link-local address is generated when device goes up + ip netns exec "${NS0}" sysctl -qw net.ipv6.conf.gretest.addr_gen_mode="${ADDR_GEN_MODE}" + ip -netns "${NS0}" link set dev gretest up + check_ipv6_ll_addr gretest "${MATCH_REGEXP}" "${XRET}" "config: ${MSG}" + + # Now disable link-local address generation + ip -netns "${NS0}" link set dev gretest down + ip netns exec "${NS0}" sysctl -qw net.ipv6.conf.gretest.addr_gen_mode=1 + ip -netns "${NS0}" link set dev gretest up + + # Check that link-local address generation works when re-enabled while + # the device is already up + ip netns exec "${NS0}" sysctl -qw net.ipv6.conf.gretest.addr_gen_mode="${ADDR_GEN_MODE}" + check_ipv6_ll_addr gretest "${MATCH_REGEXP}" "${XRET}" "update: ${MSG}" + + ip -netns "${NS0}" link del dev gretest +} + +test_gre4() +{ + local GRE_TYPE + local MODE + + for GRE_TYPE in "gre" "gretap"; do + printf "\n####\nTesting IPv6 link-local address generation on ${GRE_TYPE} devices\n####\n\n" + + for MODE in "eui64" "none" "stable-privacy" "random"; do + test_gre_device "${GRE_TYPE}" 192.0.2.10 192.0.2.11 "${MODE}" + test_gre_device "${GRE_TYPE}" any 192.0.2.11 "${MODE}" + test_gre_device "${GRE_TYPE}" 192.0.2.10 any "${MODE}" + done + done +} + +test_gre6() +{ + local GRE_TYPE + local MODE + + for GRE_TYPE in "ip6gre" "ip6gretap"; do + printf "\n####\nTesting IPv6 link-local address generation on ${GRE_TYPE} devices\n####\n\n" + + for MODE in "eui64" "none" "stable-privacy" "random"; do + test_gre_device "${GRE_TYPE}" 2001:db8::10 2001:db8::11 "${MODE}" + test_gre_device "${GRE_TYPE}" any 2001:db8::11 "${MODE}" + test_gre_device "${GRE_TYPE}" 2001:db8::10 any "${MODE}" + done + done +} + +usage() +{ + echo "Usage: $0 [-p]" + exit 1 +} + +while getopts :p o +do + case $o in + p) PAUSE_ON_FAIL="yes";; + *) usage;; + esac +done + +setup_ns NS0 + +set -e +trap exit_cleanup_all EXIT + +setup_basenet + +test_gre4 +test_gre6