On 22 Mar 2021, at 19:50, Paolo Valerio wrote:
Hi Eelco, Thanks for working on this, very useful indeed. not a full review, but I have a question about a minor thing. Eelco Chaudron <[email protected]> writes:Currently, conntrack in the kernel has an undocumented feature referredto as NULL SNAT. Basically, when a source port collision is detected during the commit, the source port will be translated to an ephemeral port. If there is no collision, no SNAT is performed. This patchset documents this behavior and adds a self-test to verify it's not changing. Signed-off-by: Eelco Chaudron <[email protected]> --- lib/ovs-actions.xml | 10 ++++++++ tests/system-kmod-macros.at | 7 ++++++tests/system-traffic.at | 45 ++++++++++++++++++++++++++++++++++++++tests/system-userspace-macros.at | 10 ++++++++ 4 files changed, 72 insertions(+) diff --git a/lib/ovs-actions.xml b/lib/ovs-actions.xml index a2778de4b..a0070e6c6 100644 --- a/lib/ovs-actions.xml +++ b/lib/ovs-actions.xml @@ -1833,6 +1833,16 @@ for <var>i</var> in [1,<var>n_members</var>]:connection, will behave the same as a bare <code>nat</code>.</p> + <p>+ For SNAT, there is a special case when the <code>src</code> IP+ address is configured as all 0's, i.e.,+ <code>nat(src=0.0.0.0)</code>. In this case, when a source port + collision is detected during the commit, the source port will be + translated to an ephemeral port. If there is no collision, no SNAT + is performed. Note that this is currently only implemented in the+ Linux kernel datapath. + </p> + <p>Open vSwitch 2.6 introduced <code>nat</code>. Linux 4.6 was the earliest upstream kernel that implemented <code>ct</code> support for diff --git a/tests/system-kmod-macros.at b/tests/system-kmod-macros.atindex 15628a7c6..38bb1c55c 100644 --- a/tests/system-kmod-macros.at +++ b/tests/system-kmod-macros.at @@ -99,6 +99,13 @@ m4_define([CHECK_CONNTRACK_FRAG_OVERLAP], # m4_define([CHECK_CONNTRACK_NAT]) +# CHECK_CONNTRACK_NULL_SNAT() +# +# Perform requirements checks for running conntrack SNAT NULL tests. +# The kernel always supports NULL SNAT, so no check is needed. +# +m4_define([CHECK_CONNTRACK_NULL_SNAT]) + # CHECK_CONNTRACK_TIMEOUT() ## Perform requirements checks for running conntrack customized timeout tests.diff --git a/tests/system-traffic.at b/tests/system-traffic.at index fb5b9a36d..1be425bb4 100644 --- a/tests/system-traffic.at +++ b/tests/system-traffic.at@@ -4433,6 +4433,51 @@ tcp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=<cleared>,dport=<cleared>),reply=(src=OVS_TRAFFIC_VSWITCHD_STOP AT_CLEANUP + +AT_SETUP([conntrack - NULL SNAT]) +AT_SKIP_IF([test $HAVE_NC = no]) +CHECK_CONNTRACK() +CHECK_CONNTRACK_NULL_SNAT() +OVS_TRAFFIC_VSWITCHD_START() + +ADD_NAMESPACES(at_ns0, at_ns1) +ADD_VETH(p0, at_ns0, br0, "10.1.1.1/24") +ADD_VETH(p1, at_ns1, br0, "10.1.1.2/24") +NS_CHECK_EXEC([at_ns0], [ip route add 172.1.1.0/24 via 10.1.1.2]) + +OVS_START_L7([at_ns1], [http]) +I noticed you use nc clients, is there any specific reason you preferredhttpd over something like: NETNS_DAEMONIZE([at_ns1], [nc -l -k 80 > /dev/null], [nc0.pid])
No specific reason other than the http server python script was used in all the other tests above.
+AT_DATA([flows.txt], [dnl +table=0,priority=30,ct_state=-trk,ip,action=ct(table=0) +table=0,priority=20,ip,nw_dst=10.1.1.0/24,actions=ct(commit,nat(src=0.0.0.0),table=10) +table=0,priority=20,ip,nw_dst=172.1.1.2,actions=ct(commit,nat(dst=10.1.1.2),table=10) +table=0,priority=10,arp,action=normal +table=0,priority=1,action=drop+table=10,priority=20,ct_state=+rpl,ip,nw_dst=10.1.1.0/24 actions=ct(table=20,nat)+table=10,priority=10,ip,nw_dst=10.1.1.0/24 actions=resubmit(,20) +table=20,priority=10,ip,nw_dst=10.1.1.1,action=1 +table=20,priority=10,ip,nw_dst=10.1.1.2,action=2 +]) +AT_CHECK([ovs-ofctl --bundle add-flows br0 flows.txt]) + +dnl - Test to make sure src nat is NOT done when not needed+NS_CHECK_EXEC([at_ns0], [echo "TEST" | nc -p 30000 10.1.1.2 80 > nc-1.log]) +AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "orig=.src=10\.1\.1\.1,"], [0], [dnl+tcp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=30000,dport=80),reply=(src=10.1.1.2,dst=10.1.1.1,sport=80,dport=30000),protoinfo=(state=TIME_WAIT) +]) + +dnl - Test to make sure src nat is done when needed+NS_CHECK_EXEC([at_ns0], [echo "TEST2" | nc -p 30001 172.1.1.2 80 > nc-2.log]) +NS_CHECK_EXEC([at_ns0], [echo "TEST3" | nc -p 30001 10.1.1.2 80 > nc-3.log]) +AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep 30001 | grep "orig=.src=10\.1\.1\.1," | sed -e 's/port=30001/port=<clnt_s_port>/g' -e 's/sport=80,dport=[[0-9]]\+/sport=80,dport=<rnd_port>/g' | sort], [0], [dnl+tcp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=<clnt_s_port>,dport=80),reply=(src=10.1.1.2,dst=10.1.1.1,sport=80,dport=<rnd_port>),protoinfo=(state=TIME_WAIT) +tcp,orig=(src=10.1.1.1,dst=172.1.1.2,sport=<clnt_s_port>,dport=80),reply=(src=10.1.1.2,dst=10.1.1.1,sport=80,dport=<clnt_s_port>),protoinfo=(state=TIME_WAIT) +]) + +OVS_TRAFFIC_VSWITCHD_STOP +AT_CLEANUP + + AT_SETUP([conntrack - simple DNAT]) CHECK_CONNTRACK() CHECK_CONNTRACK_NAT()diff --git a/tests/system-userspace-macros.at b/tests/system-userspace-macros.atindex 34f82cee3..71acc8618 100644 --- a/tests/system-userspace-macros.at +++ b/tests/system-userspace-macros.at @@ -96,6 +96,16 @@ m4_define([CHECK_CONNTRACK_FRAG_OVERLAP]) # m4_define([CHECK_CONNTRACK_NAT]) +# CHECK_CONNTRACK_NULL_SNAT() +# +# Perform requirements checks for running conntrack SNAT NULL tests. +# The userspace datapath does not support NULL SNAT. +# +m4_define([CHECK_CONNTRACK_NULL_SNAT], +[ + AT_SKIP_IF([:]) +]) + # CHECK_CONNTRACK_TIMEOUT() ## Perform requirements checks for running conntrack customized timeout tests.
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