add fallback to TCP tests (server side)

test fallback to TCP in the following conditions:
 - client sends a v0 SYN (might trigger false postitive when testing v0
   kernel)
 - client sends a SYN with mp_capable flag 'B' set
 - client sends a SYN with mp_capable flag 'H' unset
 - client flips version to v0 in the 3rd ACK
 - client flips mp_capable flag 'B' in the 3rd ACK
 - client flips mp_capable flag 'H' in the 3rd ACK

related to: issue #3

Signed-off-by: Davide Caratti <[email protected]>

gtests/net/mptcp/mp_capable/v1_bind_tcpfallback_flagB.pkt

@@ -0,0 +1,22 @@
+// test the mp_capable 'B' flag according to RFC8684 § 3.1
+`../common/defaults.sh`
+
++0    socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3
++0    setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+
++0    bind(3, ..., ...) = 0
++0    listen(3, 1) = 0
++0      < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 8,mpcapable v1 flags 0x41 nokey>
++0      > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
++0.01   < . 1:1(0) ack 1 win 257
++0    accept(3, ..., ...) = 4
+
+// ensure that traffic plane is functional and does not use DSS
+
++0    write(4, ..., 1000) = 1000
++0      > P. 1:1001(1000) ack 1
++0      < P. 1:501(500) ack 1001 win 257
++0      > . 1001:1001(0) ack 501
++0    read(4, ..., 1000) = 500
+
+

gtests/net/mptcp/mp_capable/v1_bind_tcpfallback_flagB_3rd_ack.pkt

@@ -0,0 +1,23 @@
+// Test mp_capable mptcp option, first syn sent by packetdrill
+`../common/defaults.sh`
+
++0    socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3
++0    setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+
++0    bind(3, ..., ...) = 0
++0    listen(3, 1) = 0
++0      < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7,mpcapable v1 flags[flag_h]  nokey>
++0      > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8,mpcapable v1 flags[flag_h] key[skey] >
++0.01   < . 1:1(0) ack 1 win 257 <mpcapable v1 flags [flag_b,flag_h] key[ckey=2,skey] >
++0    accept(3, ..., ...) = 4
+
+// ensure that traffic plane is functional and does not use DSS
+
++0    write(4, ..., 1000) = 1000
++0      > P. 1:1001(1000) ack 1
++0      < P. 1:501(500) ack 1001 win 257
++0      > . 1001:1001(0) ack 501
++0    read(4, ..., 1000) = 500
+
+
+

gtests/net/mptcp/mp_capable/v1_bind_tcpfallback_flagH.pkt

@@ -0,0 +1,22 @@
+// test fallback to TCP of the mp_capable 'H' flag according to RFC8684 § 3.1
+`../common/defaults.sh`
+
++0    socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3
++0    setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+
++0    bind(3, ..., ...) = 0
++0    listen(3, 1) = 0
++0      < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 8,mpcapable v1 flags 0x0 nokey>
++0      > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
++0.01   < . 1:1(0) ack 1 win 257
++0    accept(3, ..., ...) = 4
+
+// ensure that traffic plane is functional and does not use DSS
+
++0    write(4, ..., 1000) = 1000
++0      > P. 1:1001(1000) ack 1
++0      < P. 1:501(500) ack 1001 win 257
++0      > . 1001:1001(0) ack 501
++0    read(4, ..., 1000) = 500
+
+

gtests/net/mptcp/mp_capable/v1_bind_tcpfallback_flagH_3rd_ack.pkt

@@ -0,0 +1,23 @@
+// Test mp_capable mptcp option, first syn sent by packetdrill
+`../common/defaults.sh`
+
++0    socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3
++0    setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+
++0    bind(3, ..., ...) = 0
++0    listen(3, 1) = 0
++0      < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7,mpcapable v1 flags[flag_h]  nokey>
++0      > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8,mpcapable v1 flags[flag_h] key[skey] >
++0.01   < . 1:1(0) ack 1 win 257 <mpcapable v1 flags 0x0 key[ckey=2,skey] >
++0    accept(3, ..., ...) = 4
+
+// ensure that traffic plane is functional and does not use DSS
+
++0    write(4, ..., 1000) = 1000
++0      > P. 1:1001(1000) ack 1
++0      < P. 1:501(500) ack 1001 win 257
++0      > . 1001:1001(0) ack 501
++0    read(4, ..., 1000) = 500
+
+
+

gtests/net/mptcp/mp_capable/v1_bind_tcpfallback_wrongver.pkt

@@ -0,0 +1,22 @@
+// test TCP fallback in case of wrong 'version' according to RFC8684 § 3.1
+`../common/defaults.sh`
+
++0    socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3
++0    setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+
++0    bind(3, ..., ...) = 0
++0    listen(3, 1) = 0
++0      < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 8,mpcapable v1 flags 0x41 nokey>
++0      > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
++0.01   < . 1:1(0) ack 1 win 257
++0    accept(3, ..., ...) = 4
+
+// ensure that traffic plane is functional and does not use DSS
+
++0    write(4, ..., 1000) = 1000
++0      > P. 1:1001(1000) ack 1
++0      < P. 1:501(500) ack 1001 win 257
++0      > . 1001:1001(0) ack 501
++0    read(4, ..., 1000) = 500
+
+

gtests/net/mptcp/mp_capable/v1_bind_tcpfallback_wrongver_3rd_ack.pkt

@@ -0,0 +1,23 @@
+// Test mp_capable mptcp option, first syn sent by packetdrill
+`../common/defaults.sh`
+
++0    socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3
++0    setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+
++0    bind(3, ..., ...) = 0
++0    listen(3, 1) = 0
++0      < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7,mpcapable v1 flags[flag_h]  nokey>
++0      > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8,mpcapable v1 flags[flag_h] key[skey] >
++0.01   < . 1:1(0) ack 1 win 257 <mpcapable v0 flags[flag_h] key[ckey=2,skey] >
++0    accept(3, ..., ...) = 4
+
+// ensure that traffic plane is functional and does not use DSS
+
++0    write(4, ..., 1000) = 1000
++0      > P. 1:1001(1000) ack 1
++0      < P. 1:501(500) ack 1001 win 257
++0      > . 1001:1001(0) ack 501
++0    read(4, ..., 1000) = 500
+
+
+