Soft lockups have been observed on a cluster of Linux-based edge routers located in a highly dynamic environment. Using the `bird` service, these routers continuously update BGP-advertised routes due to frequently changing nexthop destinations, while also managing significant IPv6 traffic. The lockups occur during the traversal of the multipath circular linked-list in the `fib6_select_path` function, particularly while iterating through the siblings in the list. The issue typically arises when the nodes of the linked list are unexpectedly deleted concurrently on a different core—indicated by their 'next' and 'previous' elements pointing back to the node itself and their reference count dropping to zero. This results in an infinite loop, leading to a soft lockup that triggers a system panic via the watchdog timer.

Apply RCU primitives in the problematic code sections to resolve the issue. Where necessary, update the references to fib6_siblings to annotate or use the RCU APIs.

Include a test script that reproduces the issue. The script periodically updates the routing table while generating a heavy load of outgoing IPv6 traffic through multiple iperf3 clients. It consistently induces infinite soft lockups within a couple of minutes.

Kernel log:

0 [ffffbd13003e8d30] machine_kexec at ffffffff8ceaf3eb 1 [ffffbd13003e8d90] __crash_kexec at ffffffff8d0120e3 2 [ffffbd13003e8e58] panic at ffffffff8cef65d4 3 [ffffbd13003e8ed8] watchdog_timer_fn at ffffffff8d05cb03 4 [ffffbd13003e8f08] __hrtimer_run_queues at ffffffff8cfec62f 5 [ffffbd13003e8f70] hrtimer_interrupt at ffffffff8cfed756 6 [ffffbd13003e8fd0] __sysvec_apic_timer_interrupt at ffffffff8cea01af 7 [ffffbd13003e8ff0] sysvec_apic_timer_interrupt at ffffffff8df1b83d -- <IRQ stack> -- 8 [ffffbd13003d3708] asm_sysvec_apic_timer_interrupt at ffffffff8e000ecb [exception RIP: fib6_select_path+299] RIP: ffffffff8ddafe7b RSP: ffffbd13003d37b8 RFLAGS: 00000287 RAX: ffff975850b43600 RBX: ffff975850b40200 RCX: 0000000000000000 RDX: 000000003fffffff RSI: 0000000051d383e4 RDI: ffff975850b43618 RBP: ffffbd13003d3800 R8: 0000000000000000 R9: ffff975850b40200 R10: 0000000000000000 R11: 0000000000000000 R12: ffffbd13003d3830 R13: ffff975850b436a8 R14: ffff975850b43600 R15: 0000000000000007 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 9 [ffffbd13003d3808] ip6_pol_route at ffffffff8ddb030c 10 [ffffbd13003d3888] ip6_pol_route_input at ffffffff8ddb068c 11 [ffffbd13003d3898] fib6_rule_lookup at ffffffff8ddf02b5 12 [ffffbd13003d3928] ip6_route_input at ffffffff8ddb0f47 13 [ffffbd13003d3a18] ip6_rcv_finish_core.constprop.0 at ffffffff8dd950d0 14 [ffffbd13003d3a30] ip6_list_rcv_finish.constprop.0 at ffffffff8dd96274 15 [ffffbd13003d3a98] ip6_sublist_rcv at ffffffff8dd96474 16 [ffffbd13003d3af8] ipv6_list_rcv at ffffffff8dd96615 17 [ffffbd13003d3b60] __netif_receive_skb_list_core at ffffffff8dc16fec 18 [ffffbd13003d3be0] netif_receive_skb_list_internal at ffffffff8dc176b3 19 [ffffbd13003d3c50] napi_gro_receive at ffffffff8dc565b9 20 [ffffbd13003d3c80] ice_receive_skb at ffffffffc087e4f5 [ice] 21 [ffffbd13003d3c90] ice_clean_rx_irq at ffffffffc0881b80 [ice] 22 [ffffbd13003d3d20] ice_napi_poll at ffffffffc088232f [ice] 23 [ffffbd13003d3d80] __napi_poll at ffffffff8dc18000 24 [ffffbd13003d3db8] net_rx_action at ffffffff8dc18581 25 [ffffbd13003d3e40] __do_softirq at ffffffff8df352e9 26 [ffffbd13003d3eb0] run_ksoftirqd at ffffffff8ceffe47 27 [ffffbd13003d3ec0] smpboot_thread_fn at ffffffff8cf36a30 28 [ffffbd13003d3ee8] kthread at ffffffff8cf2b39f 29 [ffffbd13003d3f28] ret_from_fork at ffffffff8ce5fa64 30 [ffffbd13003d3f50] ret_from_fork_asm at ffffffff8ce03cbb

Fixes: 66f5d6ce53e6 ("ipv6: replace rwlock with rcu and spinlock in fib6_table") Reported-by: Adrian Oliver kernel@aoliver.ca Signed-off-by: Omid Ehtemam-Haghighi omid.ehtemamhaghighi@menlosecurity.com Cc: David S. Miller davem@davemloft.net Cc: David Ahern dsahern@gmail.com Cc: Eric Dumazet edumazet@google.com Cc: Jakub Kicinski kuba@kernel.org Cc: Paolo Abeni pabeni@redhat.com Cc: Shuah Khan shuah@kernel.org Cc: Ido Schimmel idosch@idosch.org Cc: Kuniyuki Iwashima kuniyu@amazon.com Cc: Simon Horman horms@kernel.org Cc: netdev@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- v5 -> v6: * Adjust the comment line lengths in the test script to a maximum of 80 characters * Change memory allocation in inet6_rt_notify from gfp_any() to GFP_ATOMIC for atomic allocation in non-blocking contexts, as suggested by Ido Schimmel * NOTE: I have executed the test script on both bare-metal servers and virtualized environments such as QEMU and vng. In the case of bare-metal, it consistently triggers a soft lockup in under a minute on unpatched kernels. For the virtualized environments, an unpatched kernel compiled with the Ubuntu 24.04 configuration also triggers a soft lockup, though it takes longer; however, it did not trigger a soft lockup on kernels compiled with configurations provided in:

https://github.com/linux-netdev/nipa/wiki/How-to-run-netdev-selftests-CI-sty...

leading to potential false negatives in the test results.

I am curious if this test can be executed on a bare-metal machine within a CI system, if such a setup exists, rather than in a virtualized environment. If that’s not possible, how can I apply a different kernel configuration, such as the one used in Ubuntu 24.04, for this test? Please advise.

v4 -> v5: * Addressed review comments from Paolo Abeni. * Added additional clarifying comments in the test script. * Minor cleanup performed in the test script.

v3 -> v4: * Added RCU primitives to rt6_fill_node(). I found that this function is typically called either with a table lock held or within rcu_read_lock/rcu_read_unlock pairs, except in the following call chain, where the protection is unclear:

rt_fill_node() fib6_info_hw_flags_set() mlxsw_sp_fib6_offload_failed_flag_set() mlxsw_sp_router_fib6_event_work()

The last function is initialized as a work item in mlxsw_sp_router_fib_event() and scheduled for deferred execution. I am unsure if the execution context of this work item is protected by any table lock or rcu_read_lock/rcu_read_unlock pair, so I have added the protection. Please let me know if this is redundant.

* Other review comments addressed

v2 -> v3: * Removed redundant rcu_read_lock()/rcu_read_unlock() pairs * Revised the test script based on Ido Schimmel's feedback * Updated the test script to ensure compatibility with the latest iperf3 version * Fixed new warnings generated with 'C=2' in the previous version * Other review comments addressed

v1 -> v2: * list_del_rcu() is applied exclusively to legacy multipath code * All occurrences of fib6_siblings have been modified to utilize RCU APIs for annotation and usage. * Additionally, a test script for reproducing the reported issue is included --- net/ipv6/ip6_fib.c | 8 +- net/ipv6/route.c | 45 ++- tools/testing/selftests/net/Makefile | 1 + .../net/ipv6_route_update_soft_lockup.sh | 262 ++++++++++++++++++ 4 files changed, 297 insertions(+), 19 deletions(-) create mode 100755 tools/testing/selftests/net/ipv6_route_update_soft_lockup.sh

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index eb111d20615c..9a1c59275a10 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -1190,8 +1190,8 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt, while (sibling) { if (sibling->fib6_metric == rt->fib6_metric && rt6_qualify_for_ecmp(sibling)) { - list_add_tail(&rt->fib6_siblings, - &sibling->fib6_siblings); + list_add_tail_rcu(&rt->fib6_siblings, + &sibling->fib6_siblings); break; } sibling = rcu_dereference_protected(sibling->fib6_next, @@ -1252,7 +1252,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt, fib6_siblings) sibling->fib6_nsiblings--; rt->fib6_nsiblings = 0; - list_del_init(&rt->fib6_siblings); + list_del_rcu(&rt->fib6_siblings); rt6_multipath_rebalance(next_sibling); return err; } @@ -1970,7 +1970,7 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn, &rt->fib6_siblings, fib6_siblings) sibling->fib6_nsiblings--; rt->fib6_nsiblings = 0; - list_del_init(&rt->fib6_siblings); + list_del_rcu(&rt->fib6_siblings); rt6_multipath_rebalance(next_sibling); }

diff --git a/net/ipv6/route.c b/net/ipv6/route.c index b4251915585f..b9b986bda943 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -413,8 +413,8 @@ void fib6_select_path(const struct net *net, struct fib6_result *res, struct flowi6 *fl6, int oif, bool have_oif_match, const struct sk_buff *skb, int strict) { - struct fib6_info *sibling, *next_sibling; struct fib6_info *match = res->f6i; + struct fib6_info *sibling;

if (!match->nh && (!match->fib6_nsiblings || have_oif_match)) goto out; @@ -440,8 +440,8 @@ void fib6_select_path(const struct net *net, struct fib6_result *res, if (fl6->mp_hash <= atomic_read(&match->fib6_nh->fib_nh_upper_bound)) goto out;

- list_for_each_entry_safe(sibling, next_sibling, &match->fib6_siblings, - fib6_siblings) { + list_for_each_entry_rcu(sibling, &match->fib6_siblings, + fib6_siblings) { const struct fib6_nh *nh = sibling->fib6_nh; int nh_upper_bound;

@@ -5195,14 +5195,18 @@ static void ip6_route_mpath_notify(struct fib6_info *rt, * nexthop. Since sibling routes are always added at the end of * the list, find the first sibling of the last route appended */ + rcu_read_lock(); + if ((nlflags & NLM_F_APPEND) && rt_last && rt_last->fib6_nsiblings) { - rt = list_first_entry(&rt_last->fib6_siblings, - struct fib6_info, - fib6_siblings); + rt = list_first_or_null_rcu(&rt_last->fib6_siblings, + struct fib6_info, + fib6_siblings); }

if (rt) inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags); + + rcu_read_unlock(); }

static bool ip6_route_mpath_should_notify(const struct fib6_info *rt) @@ -5547,17 +5551,21 @@ static size_t rt6_nlmsg_size(struct fib6_info *f6i) nexthop_for_each_fib6_nh(f6i->nh, rt6_nh_nlmsg_size, &nexthop_len); } else { - struct fib6_info *sibling, *next_sibling; struct fib6_nh *nh = f6i->fib6_nh; + struct fib6_info *sibling;

nexthop_len = 0; if (f6i->fib6_nsiblings) { rt6_nh_nlmsg_size(nh, &nexthop_len);

- list_for_each_entry_safe(sibling, next_sibling, - &f6i->fib6_siblings, fib6_siblings) { + rcu_read_lock(); + + list_for_each_entry_rcu(sibling, &f6i->fib6_siblings, + fib6_siblings) { rt6_nh_nlmsg_size(sibling->fib6_nh, &nexthop_len); } + + rcu_read_unlock(); } nexthop_len += lwtunnel_get_encap_size(nh->fib_nh_lws); } @@ -5721,7 +5729,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb, lwtunnel_fill_encap(skb, dst->lwtstate, RTA_ENCAP, RTA_ENCAP_TYPE) < 0) goto nla_put_failure; } else if (rt->fib6_nsiblings) { - struct fib6_info *sibling, *next_sibling; + struct fib6_info *sibling; struct nlattr *mp;

mp = nla_nest_start_noflag(skb, RTA_MULTIPATH); @@ -5733,14 +5741,21 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb, 0) < 0) goto nla_put_failure;

- list_for_each_entry_safe(sibling, next_sibling, - &rt->fib6_siblings, fib6_siblings) { + rcu_read_lock(); + + list_for_each_entry_rcu(sibling, &rt->fib6_siblings, + fib6_siblings) { if (fib_add_nexthop(skb, &sibling->fib6_nh->nh_common, sibling->fib6_nh->fib_nh_weight, - AF_INET6, 0) < 0) + AF_INET6, 0) < 0) { + rcu_read_unlock(); + goto nla_put_failure; + } }

+ rcu_read_unlock(); + nla_nest_end(skb, mp); } else if (rt->nh) { if (nla_put_u32(skb, RTA_NH_ID, rt->nh->id)) @@ -6177,7 +6192,7 @@ void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info, err = -ENOBUFS; seq = info->nlh ? info->nlh->nlmsg_seq : 0;

- skb = nlmsg_new(rt6_nlmsg_size(rt), gfp_any()); + skb = nlmsg_new(rt6_nlmsg_size(rt), GFP_ATOMIC); if (!skb) goto errout;

@@ -6190,7 +6205,7 @@ void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info, goto errout; } rtnl_notify(skb, net, info->portid, RTNLGRP_IPV6_ROUTE, - info->nlh, gfp_any()); + info->nlh, GFP_ATOMIC); return; errout: rtnl_set_sk_err(net, RTNLGRP_IPV6_ROUTE, err); diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile index 649f1fe0dc46..88cbac27aa10 100644 --- a/tools/testing/selftests/net/Makefile +++ b/tools/testing/selftests/net/Makefile @@ -96,6 +96,7 @@ TEST_PROGS += fdb_flush.sh TEST_PROGS += fq_band_pktlimit.sh TEST_PROGS += vlan_hw_filter.sh TEST_PROGS += bpf_offload.py +TEST_PROGS += ipv6_route_update_soft_lockup.sh

# YNL files, must be before "include ..lib.mk" EXTRA_CLEAN += $(OUTPUT)/libynl.a diff --git a/tools/testing/selftests/net/ipv6_route_update_soft_lockup.sh b/tools/testing/selftests/net/ipv6_route_update_soft_lockup.sh new file mode 100755 index 000000000000..c61a7a8352cf --- /dev/null +++ b/tools/testing/selftests/net/ipv6_route_update_soft_lockup.sh @@ -0,0 +1,262 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Testing for potential kernel soft lockup during IPv6 routing table +# refresh under heavy outgoing IPv6 traffic. If a kernel soft lockup +# occurs, a kernel panic will be triggered to prevent associated issues. +# +# +# Test Environment Layout +# +# ┌----------------┐ ┌----------------┐ +# | SOURCE_NS | | SINK_NS | +# | NAMESPACE | | NAMESPACE | +# |(iperf3 clients)| |(iperf3 servers)| +# | | | | +# | | | | +# | ┌-----------| nexthops |---------┐ | +# | |veth_source|<--------------------------------------->|veth_sink|<┐ | +# | └-----------|2001:0DB8:1::0:1/96 2001:0DB8:1::1:1/96 |---------┘ | | +# | | ^ 2001:0DB8:1::1:2/96 | | | +# | | . . | fwd | | +# | ┌---------┐ | . . | | | +# | | IPv6 | | . . | V | +# | | routing | | . 2001:0DB8:1::1:80/96| ┌-----┐ | +# | | table | | . | | lo | | +# | | nexthop | | . └--------┴-----┴-┘ +# | | update | | ............................> 2001:0DB8:2::1:1/128 +# | └-------- ┘ | +# └----------------┘ +# +# The test script sets up two network namespaces, source_ns and sink_ns, +# connected via a veth link. Within source_ns, it continuously updates the +# IPv6 routing table by flushing and inserting IPV6_NEXTHOP_ADDR_COUNT nexthop +# IPs destined for SINK_LOOPBACK_IP_ADDR in sink_ns. This refresh occurs at a +# rate of 1/ROUTING_TABLE_REFRESH_PERIOD per second for TEST_DURATION seconds. +# +# Simultaneously, multiple iperf3 clients within source_ns generate heavy +# outgoing IPv6 traffic. Each client is assigned a unique port number starting +# at 5000 and incrementing sequentially. Each client targets a unique iperf3 +# server running in sink_ns, connected to the SINK_LOOPBACK_IFACE interface +# using the same port number. +# +# The number of iperf3 servers and clients is set to half of the total +# available cores on each machine. +# +# NOTE: We have tested this script on machines with various CPU specifications, +# ranging from lower to higher performance as listed below. The test script +# effectively triggered a kernel soft lockup on machines running an unpatched +# kernel in under a minute: +# +# - 1x Intel Xeon E-2278G 8-Core Processor @ 3.40GHz +# - 1x Intel Xeon E-2378G Processor 8-Core @ 2.80GHz +# - 1x AMD EPYC 7401P 24-Core Processor @ 2.00GHz +# - 1x AMD EPYC 7402P 24-Core Processor @ 2.80GHz +# - 2x Intel Xeon Gold 5120 14-Core Processor @ 2.20GHz +# - 1x Ampere Altra Q80-30 80-Core Processor @ 3.00GHz +# - 2x Intel Xeon Gold 5120 14-Core Processor @ 2.20GHz +# - 2x Intel Xeon Silver 4214 24-Core Processor @ 2.20GHz +# - 1x AMD EPYC 7502P 32-Core @ 2.50GHz +# - 1x Intel Xeon Gold 6314U 32-Core Processor @ 2.30GHz +# - 2x Intel Xeon Gold 6338 32-Core Processor @ 2.00GHz +# +# On less performant machines, you may need to increase the TEST_DURATION +# parameter to enhance the likelihood of encountering a race condition leading +# to a kernel soft lockup and avoid a false negative result. +# +# NOTE: The test may not produce the expected result in virtualized +# environments (e.g., qemu) due to differences in timing and CPU handling, +# which can affect the conditions needed to trigger a soft lockup. + +source lib.sh +source net_helper.sh + +TEST_DURATION=300 +ROUTING_TABLE_REFRESH_PERIOD=0.01 + +IPERF3_BITRATE="300m" + + +IPV6_NEXTHOP_ADDR_COUNT="128" +IPV6_NEXTHOP_ADDR_MASK="96" +IPV6_NEXTHOP_PREFIX="2001:0DB8:1" + + +SOURCE_TEST_IFACE="veth_source" +SOURCE_TEST_IP_ADDR="2001:0DB8:1::0:1/96" + +SINK_TEST_IFACE="veth_sink" +# ${SINK_TEST_IFACE} is populated with the following range of IPv6 addresses: +# 2001:0DB8:1::1:1 to 2001:0DB8:1::1:${IPV6_NEXTHOP_ADDR_COUNT} +SINK_LOOPBACK_IFACE="lo" +SINK_LOOPBACK_IP_MASK="128" +SINK_LOOPBACK_IP_ADDR="2001:0DB8:2::1:1" + +nexthop_ip_list="" +termination_signal="" +kernel_softlokup_panic_prev_val="" + +terminate_ns_processes_by_pattern() { + local ns=$1 + local pattern=$2 + + for pid in $(ip netns pids ${ns}); do + [ -e /proc/$pid/cmdline ] && grep -qe "${pattern}" /proc/$pid/cmdline && kill -9 $pid + done +} + +cleanup() { + echo "info: cleaning up namespaces and terminating all processes within them..." + + + # Terminate iperf3 instances running in the source_ns. To avoid race + # conditions, first iterate over the PIDs and terminate those + # associated with the bash shells running the + # `while true; do iperf3 -c ...; done` loops. In a second iteration, + # terminate the individual `iperf3 -c ...` instances. + terminate_ns_processes_by_pattern ${source_ns} while + terminate_ns_processes_by_pattern ${source_ns} iperf3 + + # Repeat the same process for sink_ns + terminate_ns_processes_by_pattern ${sink_ns} while + terminate_ns_processes_by_pattern ${sink_ns} iperf3 + + # Check if any iperf3 instances are still running. This could happen + # if a core has entered an infinite loop and the timeout for detecting + # the soft lockup has not expired, but either the test interval has + # already elapsed or the test was terminated manually (e.g., with ^C) + for pid in $(ip netns pids ${source_ns}); do + if [ -e /proc/$pid/cmdline ] && grep -qe 'iperf3' /proc/$pid/cmdline; then + echo "FAIL: unable to terminate some iperf3 instances. Soft lockup is underway. A kernel panic is on the way!" + exit ${ksft_fail} + fi + done + + if [ "$termination_signal" == "SIGINT" ]; then + echo "SKIP: Termination due to ^C (SIGINT)" + elif [ "$termination_signal" == "SIGALRM" ]; then + echo "PASS: No kernel soft lockup occurred during this ${TEST_DURATION} second test" + fi + + cleanup_ns ${source_ns} ${sink_ns} + + sysctl -qw kernel.softlockup_panic=${kernel_softlokup_panic_prev_val} +} + +setup_prepare() { + setup_ns source_ns sink_ns + + ip -n ${source_ns} link add name ${SOURCE_TEST_IFACE} type veth peer name ${SINK_TEST_IFACE} netns ${sink_ns} + + # Setting up the Source namespace + ip -n ${source_ns} addr add ${SOURCE_TEST_IP_ADDR} dev ${SOURCE_TEST_IFACE} + ip -n ${source_ns} link set dev ${SOURCE_TEST_IFACE} qlen 10000 + ip -n ${source_ns} link set dev ${SOURCE_TEST_IFACE} up + ip netns exec ${source_ns} sysctl -qw net.ipv6.fib_multipath_hash_policy=1 + + # Setting up the Sink namespace + ip -n ${sink_ns} addr add ${SINK_LOOPBACK_IP_ADDR}/${SINK_LOOPBACK_IP_MASK} dev ${SINK_LOOPBACK_IFACE} + ip -n ${sink_ns} link set dev ${SINK_LOOPBACK_IFACE} up + ip netns exec ${sink_ns} sysctl -qw net.ipv6.conf.${SINK_LOOPBACK_IFACE}.forwarding=1 + + ip -n ${sink_ns} link set ${SINK_TEST_IFACE} up + ip netns exec ${sink_ns} sysctl -qw net.ipv6.conf.${SINK_TEST_IFACE}.forwarding=1 + + + # Populate nexthop IPv6 addresses on the test interface in the sink_ns + echo "info: populating ${IPV6_NEXTHOP_ADDR_COUNT} IPv6 addresses on the ${SINK_TEST_IFACE} interface ..." + for IP in $(seq 1 ${IPV6_NEXTHOP_ADDR_COUNT}); do + ip -n ${sink_ns} addr add ${IPV6_NEXTHOP_PREFIX}::$(printf "1:%x" "${IP}")/${IPV6_NEXTHOP_ADDR_MASK} dev ${SINK_TEST_IFACE}; + done + + # Preparing list of nexthops + for IP in $(seq 1 ${IPV6_NEXTHOP_ADDR_COUNT}); do + nexthop_ip_list=$nexthop_ip_list" nexthop via ${IPV6_NEXTHOP_PREFIX}::$(printf "1:%x" $IP) dev ${SOURCE_TEST_IFACE} weight 1" + done +} + + +test_soft_lockup_during_routing_table_refresh() { + # Start num_of_iperf_servers iperf3 servers in the sink_ns namespace, + # each listening on ports starting at 5001 and incrementing + # sequentially. Since iperf3 instances may terminate unexpectedly, a + # while loop is used to automatically restart them in such cases. + echo "info: starting ${num_of_iperf_servers} iperf3 servers in the sink_ns namespace ..." + for i in $(seq 1 ${num_of_iperf_servers}); do + cmd="iperf3 --bind ${SINK_LOOPBACK_IP_ADDR} -s -p $(printf '5%03d' ${i}) --rcv-timeout 200 &>/dev/null" + ip netns exec ${sink_ns} bash -c "while true; do ${cmd}; done &" &>/dev/null + done + + # Wait for the iperf3 servers to be ready + for i in $(seq ${num_of_iperf_servers}); do + port=$(printf '5%03d' ${i}); + wait_local_port_listen ${sink_ns} ${port} tcp + done + + # Continuously refresh the routing table in the background within + # the source_ns namespace + ip netns exec ${source_ns} bash -c " + while $(ip netns list | grep -q ${source_ns}); do + ip -6 route add ${SINK_LOOPBACK_IP_ADDR}/${SINK_LOOPBACK_IP_MASK} ${nexthop_ip_list}; + sleep ${ROUTING_TABLE_REFRESH_PERIOD}; + ip -6 route delete ${SINK_LOOPBACK_IP_ADDR}/${SINK_LOOPBACK_IP_MASK}; + done &" + + # Start num_of_iperf_servers iperf3 clients in the source_ns namespace, + # each sending TCP traffic on sequential ports starting at 5001. + # Since iperf3 instances may terminate unexpectedly (e.g., if the route + # to the server is deleted in the background during a route refresh), a + # while loop is used to automatically restart them in such cases. + echo "info: starting ${num_of_iperf_servers} iperf3 clients in the source_ns namespace ..." + for i in $(seq 1 ${num_of_iperf_servers}); do + cmd="iperf3 -c ${SINK_LOOPBACK_IP_ADDR} -p $(printf '5%03d' ${i}) --length 64 --bitrate ${IPERF3_BITRATE} -t 0 --connect-timeout 150 &>/dev/null" + ip netns exec ${source_ns} bash -c "while true; do ${cmd}; done &" &>/dev/null + done + + echo "info: IPv6 routing table is being updated at the rate of $(echo "1/${ROUTING_TABLE_REFRESH_PERIOD}" | bc)/s for ${TEST_DURATION} seconds ..." + echo "info: A kernel soft lockup, if detected, results in a kernel panic!" + + wait +} + +# Make sure 'iperf3' is installed, skip the test otherwise +if [ ! -x "$(command -v "iperf3")" ]; then + echo "SKIP: 'iperf3' is not installed. Skipping the test." + exit ${ksft_skip} +fi + +# Determine the number of cores on the machine +num_of_iperf_servers=$(( $(nproc)/2 )) + +# Check if we are running on a multi-core machine, skip the test otherwise +if [ "${num_of_iperf_servers}" -eq 0 ]; then + echo "SKIP: This test is not valid on a single core machine!" + exit ${ksft_skip} +fi + +# Since the kernel soft lockup we're testing causes at least one core to enter +# an infinite loop, destabilizing the host and likely affecting subsequent +# tests, we trigger a kernel panic instead of reporting a failure and +# continuing +kernel_softlokup_panic_prev_val=$(sysctl -n kernel.softlockup_panic) +sysctl -qw kernel.softlockup_panic=1 + +handle_sigint() { + termination_signal="SIGINT" + cleanup + exit ${ksft_skip} +} + +handle_sigalrm() { + termination_signal="SIGALRM" + cleanup + exit ${ksft_pass} +} + +trap handle_sigint SIGINT +trap handle_sigalrm SIGALRM + +(sleep ${TEST_DURATION} && kill -s SIGALRM $$)& + +setup_prepare +test_soft_lockup_during_routing_table_refresh