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-rw-r--r--plugins/snat-plugin/snat/in2out.c114
-rw-r--r--test/test_snat.py67
2 files changed, 181 insertions, 0 deletions
diff --git a/plugins/snat-plugin/snat/in2out.c b/plugins/snat-plugin/snat/in2out.c
index 43ee2d0e75a..d7b647ef14e 100644
--- a/plugins/snat-plugin/snat/in2out.c
+++ b/plugins/snat-plugin/snat/in2out.c
@@ -405,6 +405,108 @@ static inline u32 icmp_in2out_slow_path (snat_main_t *sm,
return next0;
}
+/**
+ * @brief Hairpinning
+ *
+ * Hairpinning allows two endpoints on the internal side of the NAT to
+ * communicate even if they only use each other's external IP addresses
+ * and ports.
+ *
+ * @param sm SNAT main.
+ * @param b0 Vlib buffer.
+ * @param ip0 IP header.
+ * @param udp0 UDP header.
+ * @param tcp0 TCP header.
+ * @param proto0 SNAT protocol.
+ */
+static inline void
+snat_hairpinning (snat_main_t *sm,
+ vlib_buffer_t * b0,
+ ip4_header_t * ip0,
+ udp_header_t * udp0,
+ tcp_header_t * tcp0,
+ u32 proto0)
+{
+ snat_session_key_t key0, sm0;
+ snat_static_mapping_key_t k0;
+ snat_session_t * s0;
+ clib_bihash_kv_8_8_t kv0, value0;
+ ip_csum_t sum0;
+ u32 new_dst_addr0 = 0, old_dst_addr0, ti = 0, si;
+ u16 new_dst_port0, old_dst_port0;
+
+ key0.addr = ip0->dst_address;
+ key0.port = udp0->dst_port;
+ key0.protocol = proto0;
+ key0.fib_index = sm->outside_fib_index;
+ kv0.key = key0.as_u64;
+
+ /* Check if destination is in active sessions */
+ if (clib_bihash_search_8_8 (&sm->out2in, &kv0, &value0))
+ {
+ /* or static mappings */
+ if (!snat_static_mapping_match(sm, key0, &sm0, 1))
+ {
+ new_dst_addr0 = sm0.addr.as_u32;
+ new_dst_port0 = sm0.port;
+ vnet_buffer(b0)->sw_if_index[VLIB_TX] = sm0.fib_index;
+ }
+ }
+ else
+ {
+ si = value0.value;
+ if (sm->num_workers > 1)
+ {
+ k0.addr = ip0->dst_address;
+ k0.port = udp0->dst_port;
+ k0.fib_index = sm->outside_fib_index;
+ kv0.key = k0.as_u64;
+ if (clib_bihash_search_8_8 (&sm->worker_by_out, &kv0, &value0))
+ ASSERT(0);
+ else
+ ti = value0.value;
+ }
+ else
+ ti = sm->num_workers;
+
+ s0 = pool_elt_at_index (sm->per_thread_data[ti].sessions, si);
+ new_dst_addr0 = s0->in2out.addr.as_u32;
+ new_dst_port0 = s0->in2out.port;
+ vnet_buffer(b0)->sw_if_index[VLIB_TX] = s0->in2out.fib_index;
+ }
+
+ /* Destination is behind the same NAT, use internal address and port */
+ if (new_dst_addr0)
+ {
+ old_dst_addr0 = ip0->dst_address.as_u32;
+ ip0->dst_address.as_u32 = new_dst_addr0;
+ sum0 = ip0->checksum;
+ sum0 = ip_csum_update (sum0, old_dst_addr0, new_dst_addr0,
+ ip4_header_t, dst_address);
+ ip0->checksum = ip_csum_fold (sum0);
+
+ old_dst_port0 = tcp0->ports.dst;
+ if (PREDICT_TRUE(new_dst_port0 != old_dst_port0))
+ {
+ if (PREDICT_TRUE(proto0 == SNAT_PROTOCOL_TCP))
+ {
+ tcp0->ports.dst = new_dst_port0;
+ sum0 = tcp0->checksum;
+ sum0 = ip_csum_update (sum0, old_dst_addr0, new_dst_addr0,
+ ip4_header_t, dst_address);
+ sum0 = ip_csum_update (sum0, old_dst_port0, new_dst_port0,
+ ip4_header_t /* cheat */, length);
+ tcp0->checksum = ip_csum_fold(sum0);
+ }
+ else
+ {
+ udp0->dst_port = new_dst_port0;
+ udp0->checksum = 0;
+ }
+ }
+ }
+}
+
static inline uword
snat_in2out_node_fn_inline (vlib_main_t * vm,
vlib_node_runtime_t * node,
@@ -594,6 +696,9 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
udp0->checksum = 0;
}
+ /* Hairpinning */
+ snat_hairpinning (sm, b0, ip0, udp0, tcp0, proto0);
+
/* Accounting */
s0->last_heard = now;
s0->total_pkts++;
@@ -739,6 +844,9 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
udp1->checksum = 0;
}
+ /* Hairpinning */
+ snat_hairpinning (sm, b1, ip1, udp1, tcp1, proto1);
+
/* Accounting */
s1->last_heard = now;
s1->total_pkts++;
@@ -919,6 +1027,9 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
udp0->checksum = 0;
}
+ /* Hairpinning */
+ snat_hairpinning (sm, b0, ip0, udp0, tcp0, proto0);
+
/* Accounting */
s0->last_heard = now;
s0->total_pkts++;
@@ -1430,6 +1541,9 @@ snat_in2out_fast_static_map_fn (vlib_main_t * vm,
}
}
+ /* Hairpinning */
+ snat_hairpinning (sm, b0, ip0, udp0, tcp0, proto0);
+
trace0:
if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE)
&& (b0->flags & VLIB_BUFFER_IS_TRACED)))
diff --git a/test/test_snat.py b/test/test_snat.py
index e90d9c0b71d..5cc76f6c7da 100644
--- a/test/test_snat.py
+++ b/test/test_snat.py
@@ -34,6 +34,9 @@ class TestSNAT(VppTestCase):
i.config_ip4()
i.resolve_arp()
+ cls.pg0.generate_remote_hosts(2)
+ cls.pg0.configure_ipv4_neighbors()
+
cls.overlapping_interfaces = list(list(cls.pg_interfaces[4:7]))
for i in cls.overlapping_interfaces:
@@ -526,6 +529,70 @@ class TestSNAT(VppTestCase):
capture = self.pg6.get_capture()
self.verify_capture_in(capture, self.pg6)
+ def test_hairpinning(self):
+ """ SNAT hairpinning """
+
+ host = self.pg0.remote_hosts[0]
+ server = self.pg0.remote_hosts[1]
+ host_in_port = 1234
+ host_out_port = 0
+ server_in_port = 5678
+ server_out_port = 8765
+
+ self.snat_add_address(self.snat_addr)
+ self.vapi.snat_interface_add_del_feature(self.pg0.sw_if_index)
+ self.vapi.snat_interface_add_del_feature(self.pg1.sw_if_index,
+ is_inside=0)
+ # add static mapping for server
+ self.snat_add_static_mapping(server.ip4, self.snat_addr,
+ server_in_port, server_out_port)
+
+ # send packet from host to server
+ p = (Ether(src=host.mac, dst=self.pg0.local_mac) /
+ IP(src=host.ip4, dst=self.snat_addr) /
+ TCP(sport=host_in_port, dport=server_out_port))
+ self.pg0.add_stream(p)
+ self.pg_enable_capture(self.pg_interfaces)
+ self.pg_start()
+ capture = self.pg0.get_capture()
+ self.assertEqual(1, len(capture))
+ p = capture[0]
+ try:
+ ip = p[IP]
+ tcp = p[TCP]
+ self.assertEqual(ip.src, self.snat_addr)
+ self.assertEqual(ip.dst, server.ip4)
+ self.assertNotEqual(tcp.sport, host_in_port)
+ self.assertEqual(tcp.dport, server_in_port)
+ host_out_port = tcp.sport
+ except:
+ error("Unexpected or invalid packet:")
+ error(p.show())
+ raise
+
+ # send reply from server to host
+ p = (Ether(src=server.mac, dst=self.pg0.local_mac) /
+ IP(src=server.ip4, dst=self.snat_addr) /
+ TCP(sport=server_in_port, dport=host_out_port))
+ self.pg0.add_stream(p)
+ self.pg_enable_capture(self.pg_interfaces)
+ self.pg_start()
+ capture = self.pg0.get_capture()
+ self.assertEqual(1, len(capture))
+ p = capture[0]
+ try:
+ ip = p[IP]
+ tcp = p[TCP]
+ self.assertEqual(ip.src, self.snat_addr)
+ self.assertEqual(ip.dst, host.ip4)
+ self.assertEqual(tcp.sport, server_out_port)
+ self.assertEqual(tcp.dport, host_in_port)
+ except:
+ error("Unexpected or invalid packet:")
+ error(p.show())
+ raise
+
+
def tearDown(self):
super(TestSNAT, self).tearDown()
if not self.vpp_dead: