added resubmit example

examples/README.md

@@ -13,7 +13,8 @@ included:
 - `register`: how to use registers in P4 and read / write the state from the
   control plane
 - `counter`: how to use counters in P4
-- `action_profile`: how to use action profiles in P4, using ECMP has support
+- `action_profile`: how to use action profiles in P4, using ECMP as support
+- `resubmit`: how to resubmit packets to the ingress pipelines
 
 All examples are orgranized the same way, with a `p4src` directory containing
 the P4 source code, and a `README` file describing the P4 program and explaining

examples/resubmit/README.md

@@ -0,0 +1,28 @@
+# Resubmit
+
+## Description
+
+This program illustrates as simply as possible how to use the `resubmit()`
+primitive. This primitive is used to make a packet go twice through the ingress
+pipeline. For more information, please refer to the P4 specification.
+
+The P4 program only consists of an ingress pipeline, with 2 tables:
+`t_ingress_1` and `t_ingress_2`. When a packet enters the pipeline, the
+following happens (based on the P4 program and the [commands.txt] (commands.txt)
+files):
+- the packet hits `table_ingress_1` and the egress port is set to 2.
+- the packet hits `table_ingress_2`, `mymeta.f1` is set to 1 and the
+  `resubmit()` primitive is called. Because `mymeta` is resubmitted along with
+  the packet, `mymeta.f1` will now be equal to 1 for the second pass.
+- the packet hits `table_ingress_1`, this time the egress port is set to 3.
+- the packet hits `table_ingress_2` which is a no-op.
+
+### Running the demo
+
+We provide a small demo to let you test the program. It consists of the
+following scripts, which you need to run one after the other, in 2 separate
+terminals:
+- [run_switch.sh] (run_switch.sh): compile the P4 program and starts the switch,
+  also configures the data plane by running the CLI [commands] (commands.txt).
+- [send_and_receive.py] (send_and_receive.py): send a packet on port 0 (veth1),
+  wait for the forwarded packet on port 3 (veth7).

examples/resubmit/commands.txt

@@ -0,0 +1,5 @@
+table_set_default t_ingress_1 _nop
+table_set_default t_ingress_2 _nop
+table_add t_ingress_1 set_port 0 => 2
+table_add t_ingress_1 set_port 1 => 3
+table_add t_ingress_2 _resubmit 0 =>

examples/resubmit/p4src/resubmit.p4

@@ -0,0 +1,101 @@
+/*
+Copyright 2013-present Barefoot Networks, Inc. 
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+header_type ethernet_t {
+    fields {
+        dstAddr : 48;
+        srcAddr : 48;
+        etherType : 16;
+    }
+}
+
+header_type intrinsic_metadata_t {
+    fields {
+        mcast_grp : 4;
+        egress_rid : 4;
+        mcast_hash : 16;
+        lf_field_list : 32;
+        resubmit_flag : 16;
+    }
+}
+
+header_type mymeta_t {
+    fields {
+        f1 : 8;
+    }
+}
+
+header ethernet_t ethernet;
+metadata intrinsic_metadata_t intrinsic_metadata;
+metadata mymeta_t mymeta;
+
+parser start {
+    return parse_ethernet;
+}
+
+parser parse_ethernet {
+    extract(ethernet);
+    return ingress;
+}
+
+action _drop() {
+    drop();
+}
+
+action _nop() {
+}
+
+action set_port(port) {
+    modify_field(standard_metadata.egress_spec, port);
+}
+
+field_list resubmit_FL {
+    standard_metadata;
+    mymeta;
+}
+
+action _resubmit() {
+    modify_field(mymeta.f1, 1);
+    resubmit(resubmit_FL);
+}
+
+table t_ingress_1 {
+    reads {
+        mymeta.f1 : exact;
+    }
+    actions {
+        _nop; set_port;
+    }
+    size : 128;
+}
+
+table t_ingress_2 {
+    reads {
+        mymeta.f1 : exact;
+    }
+    actions {
+        _nop; _resubmit;
+    }
+    size : 128;
+}
+
+control ingress {
+    apply(t_ingress_1);
+    apply(t_ingress_2);
+}
+
+control egress {
+}

examples/resubmit/run_switch.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+
+# Copyright 2013-present Barefoot Networks, Inc. 
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+THIS_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
+
+source $THIS_DIR/../env.sh
+
+P4C_BM_SCRIPT=$P4C_BM_PATH/p4c_bm/__main__.py
+
+SWITCH_PATH=$BMV2_PATH/targets/simple_switch/simple_switch
+
+CLI_PATH=$BMV2_PATH/targets/simple_switch/sswitch_CLI
+
+# Probably not very elegant but it works nice here: we enable interactive mode
+# to be able to use fg. We start the switch in the background, sleep for 2
+# minutes to give it time to start, then add the entries and put the switch
+# process back in the foreground
+set -m
+$P4C_BM_SCRIPT p4src/resubmit.p4 --json resubmit.json
+sudo echo "sudo" > /dev/null
+sudo $BMV2_PATH/targets/simple_switch/simple_switch resubmit.json \
+    -i 0@veth0 -i 1@veth2 -i 2@veth4 -i 3@veth6 -i 4@veth8 \
+    --nanolog ipc:///tmp/bm-0-log.ipc --log-console \
+    --pcap &
+sleep 2
+$CLI_PATH resubmit.json < commands.txt
+echo "READY!!!"
+fg

examples/resubmit/send_and_receive.py

@@ -0,0 +1,29 @@
+from scapy.all import *
+import sys
+import threading
+
+
+class Receiver(threading.Thread):
+    def __init__(self):
+        threading.Thread.__init__(self)
+
+    def received(self, p):
+        print "Received packet on port 3, exiting"
+        sys.exit(0)
+
+    def run(self):
+        sniff(iface="veth7", prn=lambda x: self.received(x))
+
+
+def main():
+    Receiver().start()
+
+    p = Ether(src="aa:aa:aa:aa:aa:aa") / IP(dst="10.0.1.10") / TCP() / "aaaaaaaaaaaaaaaaaaa"
+
+    print "Sending packet on port 0, listening on port 3"
+    time.sleep(1)
+    sendp(p, iface="veth1", verbose=0)
+
+
+if __name__ == '__main__':
+    main()