gso: do not gro on small packets

This has two benefits: fix an issue where small packets can be
padded to 64 bytes by the ethernet layer, and we included these bytes
in the tcp stream; and also if we receive a small packet, it signals
that this tcp stream is likely more latency-sensitive than throughput-
sensitive, and skipping gro buffering should be beneficial.

Type: fix
Change-Id: I165b97673d8cdce95ebf0a66c362ae9f9e6f3f34
Signed-off-by: Aloys Augustin <aloaugus@cisco.com>

1 files changed, 102 insertions, 0 deletions

diff --git a/test/test_gro.py b/test/test_gro.py
index 33215d65fa7..6c68299d7f4 100644
--- a/test/test_gro.py
+++ b/test/test_gro.py
@@ -138,5 +138,107 @@ class TestGRO(VppTestCase):
             self.assertEqual(rx[TCP].sport, 1234)
             self.assertEqual(rx[TCP].dport, 4321)
 
+        #
+        # Same test with IPv6
+        #
+        p = []
+        s = 0
+        for n in range(0, 88):
+            p.append((Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
+                      IPv6(src=self.pg0.remote_ip6, dst=self.pg2.remote_ip6) /
+                      TCP(sport=1234, dport=4321, seq=s, ack=n, flags='A') /
+                      Raw(b'\xa5' * 1460)))
+            s += 1460
+        p[-1][TCP].flags = 'AP'  # push to flush second packet
+
+        rxs = self.send_and_expect(self.pg0, p, self.pg2, n_rx=2)
+
+        i = 0
+        for rx in rxs:
+            i += 1
+            self.assertEqual(rx[Ether].src, self.pg2.local_mac)
+            self.assertEqual(rx[Ether].dst, self.pg2.remote_mac)
+            self.assertEqual(rx[IPv6].src, self.pg0.remote_ip6)
+            self.assertEqual(rx[IPv6].dst, self.pg2.remote_ip6)
+            self.assertEqual(rx[IPv6].plen, 64260)  # 1460 * 44 + 20 < 65536
+            self.assertEqual(rx[TCP].sport, 1234)
+            self.assertEqual(rx[TCP].dport, 4321)
+            self.assertEqual(rx[TCP].ack, (44*i - 1))
+
+        #
+        # Send a series of 1500 bytes packets each followed by a packet with a
+        # PSH flag. Verify that GRO stops everytime a PSH flag is encountered
+        #
+        p = []
+        s = 0
+        for n in range(0, n_packets):
+            p.append((Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
+                      IP(src=self.pg0.remote_ip4, dst=self.pg2.remote_ip4,
+                         flags='DF') /
+                      TCP(sport=1234, dport=4321, seq=s, ack=2*n, flags='A') /
+                      Raw(b'\xa5' * 1460)))
+            s += 1460
+            p.append((Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
+                      IP(src=self.pg0.remote_ip4, dst=self.pg2.remote_ip4,
+                         flags='DF') /
+                      TCP(sport=1234, dport=4321, seq=s, ack=2*n+1,
+                          flags='AP') /
+                      Raw(b'\xa5' * 1340)))
+            s += 1340
+
+        rxs = self.send_and_expect(self.pg0, p, self.pg2, n_rx=n_packets)
+
+        i = 0
+        for rx in rxs:
+            self.assertEqual(rx[Ether].src, self.pg2.local_mac)
+            self.assertEqual(rx[Ether].dst, self.pg2.remote_mac)
+            self.assertEqual(rx[IP].src, self.pg0.remote_ip4)
+            self.assertEqual(rx[IP].dst, self.pg2.remote_ip4)
+            self.assertEqual(rx[IP].len, 40 + 1460 + 1340)
+            self.assertEqual(rx[TCP].sport, 1234)
+            self.assertEqual(rx[TCP].dport, 4321)
+            self.assertEqual(rx[TCP].ack, (2*i + 1))
+            i += 1
+
+        #
+        # Send a series of 1500 bytes packets each followed by a short packet
+        # with padding. Verify that GRO removes the padding and stops on short
+        # packets
+        #
+        p = []
+        s = 0
+        for n in range(0, n_packets):
+            i = self.pg0
+            p.append((Ether(src=i.remote_mac, dst=i.local_mac) /
+                      IP(src=i.remote_ip4, dst=self.pg2.remote_ip4,
+                         flags='DF') /
+                      TCP(sport=1234, dport=4321, seq=s, ack=2*n, flags='A') /
+                      Raw(b'\xa5' * 1459)))
+            s += 1459
+            p2 = (Ether(src=i.remote_mac, dst=i.local_mac) /
+                  IP(src=i.remote_ip4, dst=self.pg2.remote_ip4,
+                     flags='DF', len=41) /
+                  TCP(sport=1234, dport=4321, seq=s, ack=2*n+1, flags='A') /
+                  Raw(b'\xa5'))
+            # first compute csum of pkt w/o padding to work around scapy bug
+            p2 = Ether(bytes(p2))
+            p.append(p2 / Raw(b'\xa5' * 5))  # 1 byte data + 5 bytes padding
+            s += 1
+
+        rxs = self.send_and_expect(self.pg0, p, self.pg2, n_rx=n_packets)
+
+        i = 0
+        for rx in rxs:
+            self.assertEqual(rx[Ether].src, self.pg2.local_mac)
+            self.assertEqual(rx[Ether].dst, self.pg2.remote_mac)
+            self.assertEqual(rx[IP].src, self.pg0.remote_ip4)
+            self.assertEqual(rx[IP].dst, self.pg2.remote_ip4)
+            self.assertEqual(rx[IP].len, 40 + 1459 + 1)
+            self.assertEqual(rx[TCP].sport, 1234)
+            self.assertEqual(rx[TCP].dport, 4321)
+            self.assertEqual(rx[TCP].ack, (2*i + 1))
+            i += 1
+
+
 if __name__ == '__main__':
     unittest.main(testRunner=VppTestRunner)