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

From: Anton Protopopov <[email-masked]>
Date: Sun, 24 Mar 2024 15:04:09 +0000

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.

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);
> 
>