[test] add expect tests for pcap receiving (#5043)

This adds expect tests for testing the pcap receiving function of
promiscuous mode. Also makes otLinkSetPromiscuous be called before
otLinkSetPcapCallback so that the callback won't be set when
promiscuous mode fails to start.

tests/scripts/expect/cli-2-nodes.exp

@@ -53,11 +53,10 @@ proc wait_for {command expected} {
 set timeout 1
 spawn $env(OT_COMMAND) 1
 set spawn_1 $spawn_id
-expect_after {
-    timeout { exit 1 }
-}
 spawn $env(OT_COMMAND) 2
 set spawn_2 $spawn_id
+spawn $env(OT_COMMAND) 3
+set spawn_3 $spawn_id
 expect_after {
     timeout { exit 1 }
 }
@@ -84,6 +83,10 @@ expect "Done"
 expect "Commissioner: active"
 send "commissioner joiner add $eui64 $psk\n"
 expect "Done"
+send "channel\n"
+expect -re {(\d+)}
+set channel $expect_out(1,string)
+expect "Done"
 
 set spawn_id $spawn_2
 send "mode rs\n"
@@ -97,6 +100,12 @@ send "thread start\n"
 expect "Done"
 wait_for "state" "child"
 
+set spawn_id $spawn_3
+send "channel $channel\n"
+expect "Done"
+send "promiscuous enable\n"
+expect "Done"
+
 
 # ping
 set spawn_id $spawn_2
@@ -107,12 +116,19 @@ set addr $expect_out(1,string)
 set spawn_id $spawn_1
 send "ping $addr\n"
 expect "16 bytes from $addr: icmp_seq=1"
-send "ping $addr 20 10 0.123456 255\n"
+send "ping $addr 20 10 0.00123456 255\n"
 for {set i 2} {$i <= 11} {incr i} {
     expect "28 bytes from $addr: icmp_seq=$i"
 }
 
 
+# pcap receive
+set spawn_id $spawn_3
+expect -re {={44}\[len =\s+\d+]={28}}
+expect -re {\|( ([0-9A-Z]{2}|\.\.)){16}\|( .){16}\|}
+expect -re {-{83}}
+
+
 # child
 set spawn_id $spawn_2
 send "extaddr\n"