Subject: Re: [PATCH v1 bpf-next 2/2] selftests/bpf: Add BPF_FIB_LOOKUP_MARK tests

From: Martin KaFai Lau <[email-masked]>
Date: Mon, 25 Mar 2024 11:12:39 -0700

On 3/24/24 8:04 AM, Anton Protopopov wrote:
> On Sat, Mar 23, 2024 at 03:34:10PM -0700, Martin KaFai Lau wrote:
>> On 3/22/24 7:02 AM, Anton Protopopov wrote:
>>> This patch extends the fib_lookup test suite by adding a few test
>>> cases for each IP family to test the new BPF_FIB_LOOKUP_MARK flag
>>> to the bpf_fib_lookup:
>>>
>>>     * Test destination IP address selection with and without a mark
>>>       and/or the BPF_FIB_LOOKUP_MARK flag set
>>>
>>> To test this functionality another network namespace and a new veth
>>> pair were added to the test.
>>>
>>
>> [ ... ]
>>
>>>    static const struct fib_lookup_test tests[] = {
>>> @@ -90,10 +105,47 @@ static const struct fib_lookup_test tests[] = {
>>>    	  .daddr = IPV6_ADDR_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>>    	  .expected_src = IPV6_IFACE_ADDR_SEC,
>>>    	  .lookup_flags = BPF_FIB_LOOKUP_SRC | BPF_FIB_LOOKUP_SKIP_NEIGH, },
>>> +	/* policy routing */
>>> +	{ .desc = "IPv4 policy routing, default",
>>> +	  .daddr = IPV4_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV4_GW1, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_MARK | BPF_FIB_LOOKUP_SKIP_NEIGH, },
>>> +	{ .desc = "IPv4 policy routing, mark doesn't point to a policy",
>>> +	  .daddr = IPV4_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV4_GW1, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_MARK | BPF_FIB_LOOKUP_SKIP_NEIGH,
>>> +	  .mark = MARK_NO_POLICY, },
>>> +	{ .desc = "IPv4 policy routing, mark points to a policy",
>>> +	  .daddr = IPV4_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV4_GW2, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_MARK | BPF_FIB_LOOKUP_SKIP_NEIGH,
>>> +	  .mark = MARK, },
>>> +	{ .desc = "IPv4 policy routing, mark points to a policy, but no flag",
>>> +	  .daddr = IPV4_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV4_GW1, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH,
>>> +	  .mark = MARK, },
>>> +	{ .desc = "IPv6 policy routing, default",
>>> +	  .daddr = IPV6_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV6_GW1, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_MARK | BPF_FIB_LOOKUP_SKIP_NEIGH, },
>>> +	{ .desc = "IPv6 policy routing, mark doesn't point to a policy",
>>> +	  .daddr = IPV6_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV6_GW1, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_MARK | BPF_FIB_LOOKUP_SKIP_NEIGH,
>>> +	  .mark = MARK_NO_POLICY, },
>>> +	{ .desc = "IPv6 policy routing, mark points to a policy",
>>> +	  .daddr = IPV6_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV6_GW2, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_MARK | BPF_FIB_LOOKUP_SKIP_NEIGH,
>>> +	  .mark = MARK, },
>>> +	{ .desc = "IPv6 policy routing, mark points to a policy, but no flag",
>>> +	  .daddr = IPV6_REMOTE_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
>>> +	  .expected_dst = IPV6_GW1, .ifname = "veth3",
>>> +	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH,
>>> +	  .mark = MARK, },
>>>    };
>>> -static int ifindex;
>>> -
>>>    static int setup_netns(void)
>>>    {
>>>    	int err;
>>> @@ -144,12 +196,40 @@ static int setup_netns(void)
>>>    	if (!ASSERT_OK(err, "write_sysctl(net.ipv6.conf.veth1.forwarding)"))
>>>    		goto fail;
>>> +	/* Setup for policy routing tests */
>>> +	SYS(fail, "ip link add veth3 type veth peer name veth4");
>>> +	SYS(fail, "ip link set dev veth3 up");
>>> +	SYS(fail, "ip link set dev veth4 netns %s up", NS_REMOTE);
>>> +
>>> +	SYS(fail, "ip addr add %s/24 dev veth3", IPV4_LOCAL);
>>> +	SYS(fail, "ip netns exec %s ip addr add %s/24 dev veth4", NS_REMOTE, IPV4_GW1);
>>> +	SYS(fail, "ip netns exec %s ip addr add %s/24 dev veth4", NS_REMOTE, IPV4_GW2);
>>> +	SYS(fail, "ip addr add %s/64 dev veth3 nodad", IPV6_LOCAL);
>>> +	SYS(fail, "ip netns exec %s ip addr add %s/64 dev veth4 nodad", NS_REMOTE, IPV6_GW1);
>>> +	SYS(fail, "ip netns exec %s ip addr add %s/64 dev veth4 nodad", NS_REMOTE, IPV6_GW2);
>>
>> Trying to see if the setup can be simplified.
>>
>> Does it need to add another netns and setup a reachable IPV[46]_GW[12] gateway?
>>
>> The test is not sending any traffic and it is a BPF_FIB_LOOKUP_SKIP_NEIGH test.
> 
> I think this will not work without another namespace, as FIB lookup will
> return DST="final destination", not DST="gateway", as the gateway is in the
> same namespace and can be skipped.

hmm... not sure I understand why it would get "final destination". Am I missing something?
To be specific, there is no need to configure the IPV[46]_GW[12] address:

-	SYS(fail, "ip link set dev veth4 netns %s up", NS_REMOTE);

	SYS(fail, "ip addr add %s/24 dev veth3", IPV4_LOCAL);
-	SYS(fail, "ip netns exec %s ip addr add %s/24 dev veth4", NS_REMOTE, IPV4_GW1);
-	SYS(fail, "ip netns exec %s ip addr add %s/24 dev veth4", NS_REMOTE, IPV4_GW2);
	SYS(fail, "ip addr add %s/64 dev veth3 nodad", IPV6_LOCAL);
-	SYS(fail, "ip netns exec %s ip addr add %s/64 dev veth4 nodad", NS_REMOTE, IPV6_GW1);
-	SYS(fail, "ip netns exec %s ip addr add %s/64 dev veth4 nodad", NS_REMOTE, IPV6_GW2);
	SYS(fail, "ip route add %s/32 via %s", IPV4_REMOTE_DST, IPV4_GW1);
	SYS(fail, "ip route add %s/32 via %s table %s", IPV4_REMOTE_DST, IPV4_GW2, MARK_TABLE);
	SYS(fail, "ip -6 route add %s/128 via %s", IPV6_REMOTE_DST, IPV6_GW1);
	SYS(fail, "ip -6 route add %s/128 via %s table %s", IPV6_REMOTE_DST, IPV6_GW2, MARK_TABLE);
	SYS(fail, "ip rule add prio 2 fwmark %d lookup %s", MARK, MARK_TABLE);
	SYS(fail, "ip -6 rule add prio 2 fwmark %d lookup %s", MARK, MARK_TABLE);

[root@arch-fb-vm1 ~]# ip netns exec fib_lookup_ns /bin/bash

[root@arch-fb-vm1 ~]# ip -6 rule
0:	from all lookup local
2:	from all fwmark 0x2a lookup 200
32766:	from all lookup main

[root@arch-fb-vm1 ~]# ip -6 route show table main
be:ef::b0:10 via fd01::1 dev veth3 metric 1024 linkdown pref medium

[root@arch-fb-vm1 ~]# ip -6 route show table 200
be:ef::b0:10 via fd01::2 dev veth3 metric 1024 linkdown pref medium

[root@arch-fb-vm1 ~]# ip -6 route get be:ef::b0:10
be:ef::b0:10 from :: via fd01::1 dev veth3 src fd01::3 metric 1024 pref medium

[root@arch-fb-vm1 ~]# ip -6 route get be:ef::b0:10 mark 0x2a
be:ef::b0:10 from :: via fd01::2 dev veth3 table 200 src fd01::3 metric 1024 pref medium

> 
> Instead of adding a new namespace I can move the second interface to the
> root namespace. This will work, but then we're interfering with the root
> namespace.
> 
>>> +	SYS(fail, "ip route add %s/32 via %s", IPV4_REMOTE_DST, IPV4_GW1);
>>> +	SYS(fail, "ip route add %s/32 via %s table %s", IPV4_REMOTE_DST, IPV4_GW2, MARK_TABLE);
>>> +	SYS(fail, "ip -6 route add %s/128 via %s", IPV6_REMOTE_DST, IPV6_GW1);
>>> +	SYS(fail, "ip -6 route add %s/128 via %s table %s", IPV6_REMOTE_DST, IPV6_GW2, MARK_TABLE);
>>> +	SYS(fail, "ip rule add prio 2 fwmark %d lookup %s", MARK, MARK_TABLE);
>>> +	SYS(fail, "ip -6 rule add prio 2 fwmark %d lookup %s", MARK, MARK_TABLE);
>>> +
>>> +	err = write_sysctl("/proc/sys/net/ipv4/conf/veth3/forwarding", "1");
>>> +	if (!ASSERT_OK(err, "write_sysctl(net.ipv4.conf.veth3.forwarding)"))
>>> +		goto fail;
>>> +
>>> +	err = write_sysctl("/proc/sys/net/ipv6/conf/veth3/forwarding", "1");
>>> +	if (!ASSERT_OK(err, "write_sysctl(net.ipv6.conf.veth3.forwarding)"))
>>> +		goto fail;
>>> +
>>>    	return 0;
>>>    fail:
>>>    	return -1;
>>>    }
>>
>> [ ... ]
>>
>>> @@ -248,6 +337,7 @@ void test_fib_lookup(void)
>>>    	prog_fd = bpf_program__fd(skel->progs.fib_lookup);
>>>    	SYS(fail, "ip netns add %s", NS_TEST);
>>> +	SYS(fail, "ip netns add %s", NS_REMOTE);
>>
>>