Subject: [PATCH net-next 8/9] selftests: drv-net: gro: add test for packet ordering

From: Jakub Kicinski <[email-masked]>
Date: Thu, 5 Feb 2026 14:05:40 -0800

Add a test to check if the NIC reorders packets if the hit GRO.

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 tools/testing/selftests/net/lib/gro.c         | 38 +++++++++++++++++--
 .../selftests/drivers/net/hw/gro_hw.py        | 29 ++++++++++++--
 2 files changed, 61 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/net/lib/gro.c b/tools/testing/selftests/net/lib/gro.c
index d37676c009e8..3d3312b37248 100644
--- a/tools/testing/selftests/net/lib/gro.c
+++ b/tools/testing/selftests/net/lib/gro.c
@@ -131,6 +131,7 @@ static int ethhdr_proto = -1;
 static bool ipip;
 static uint64_t txtime_ns;
 static int num_flows = 4;
+static bool order_check;
 
 #define CAPACITY_PAYLOAD_LEN 200
 
@@ -1134,6 +1135,7 @@ static void check_capacity_pkts(int fd)
 	static char buffer[IP_MAXPACKET + ETH_HLEN + 1];
 	struct iphdr *iph = (struct iphdr *)(buffer + ETH_HLEN);
 	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buffer + ETH_HLEN);
+	int num_pkt = 0, num_coal = 0, pkt_idx;
 	const char *fail_reason = NULL;
 	int flow_order[num_flows * 2];
 	int coalesced[num_flows];
@@ -1142,8 +1144,6 @@ static void check_capacity_pkts(int fd)
 	int total_data = 0;
 	int pkt_size = -1;
 	int data_len = 0;
-	int num_pkt = 0;
-	int num_coal = 0;
 	int flow_id;
 	int sport;
 
@@ -1201,6 +1201,34 @@ static void check_capacity_pkts(int fd)
 		total_data += data_len;
 	}
 
+	/* Check flow ordering. We expect to see all non-coalesced first segs
+	 * then interleaved coalesced and non-coalesced second frames.
+	 */
+	pkt_idx = 0;
+	for (flow_id = 0; order_check && flow_id < num_flows; flow_id++) {
+		bool coaled = coalesced[flow_id] > CAPACITY_PAYLOAD_LEN;
+
+		if (coaled)
+			continue;
+
+		if (flow_order[pkt_idx] != flow_id) {
+			vlog("Flow order mismatch (non-coalesced) at position %d: expected flow %d, got flow %d\n",
+			     pkt_idx, flow_id, flow_order[pkt_idx]);
+			fail_reason = fail_reason ?: "bad packet order (1)";
+		}
+		pkt_idx++;
+	}
+	for (flow_id = 0; order_check && flow_id < num_flows; flow_id++) {
+		bool coaled = coalesced[flow_id] > CAPACITY_PAYLOAD_LEN;
+
+		if (flow_order[pkt_idx] != flow_id) {
+			vlog("Flow order mismatch at position %d: expected flow %d, got flow %d, coalesced: %d\n",
+			     pkt_idx, flow_id, flow_order[pkt_idx], coaled);
+			fail_reason = fail_reason ?: "bad packet order (2)";
+		}
+		pkt_idx++;
+	}
+
 	if (!fail_reason) {
 		vlog("All %d flows coalesced correctly\n", num_flows);
 		printf("Test succeeded\n\n");
@@ -1614,12 +1642,13 @@ static void parse_args(int argc, char **argv)
 		{ "saddr", required_argument, NULL, 's' },
 		{ "smac", required_argument, NULL, 'S' },
 		{ "test", required_argument, NULL, 't' },
+		{ "order-check", no_argument, NULL, 'o' },
 		{ "verbose", no_argument, NULL, 'v' },
 		{ 0, 0, 0, 0 }
 	};
 	int c;
 
-	while ((c = getopt_long(argc, argv, "46d:D:ei:n:rs:S:t:v", opts, NULL)) != -1) {
+	while ((c = getopt_long(argc, argv, "46d:D:ei:n:rs:S:t:ov", opts, NULL)) != -1) {
 		switch (c) {
 		case '4':
 			proto = PF_INET;
@@ -1658,6 +1687,9 @@ static void parse_args(int argc, char **argv)
 		case 't':
 			testname = optarg;
 			break;
+		case 'o':
+			order_check = true;
+			break;
 		case 'v':
 			verbose = true;
 			break;
diff --git a/tools/testing/selftests/drivers/net/hw/gro_hw.py b/tools/testing/selftests/drivers/net/hw/gro_hw.py
index 3bca19e8f339..18a3b1bceefd 100755
--- a/tools/testing/selftests/drivers/net/hw/gro_hw.py
+++ b/tools/testing/selftests/drivers/net/hw/gro_hw.py
@@ -10,7 +10,7 @@ import glob
 import re
 
 from lib.py import ksft_run, ksft_exit, ksft_pr
-from lib.py import ksft_eq, ksft_ge
+from lib.py import ksft_eq, ksft_ge, ksft_variants
 from lib.py import NetDrvEpEnv, NetdevFamily
 from lib.py import KsftSkipEx
 from lib.py import bkg, cmd, defer, ethtool, ip
@@ -78,7 +78,8 @@ GRO_DPORT = 8000
     return test_queue

-def _run_gro_test(cfg, test_name, num_flows=None, ignore_fail=False):
+def _run_gro_test(cfg, test_name, num_flows=None, ignore_fail=False,
+                  order_check=False):
     """Run gro binary with given test and return output."""
     if not hasattr(cfg, "bin_remote"):
         cfg.bin_local = cfg.net_lib_dir / "gro"
@@ -98,6 +99,8 @@ GRO_DPORT = 8000
     ]
     if num_flows:
         base_args.append(f"--num-flows {num_flows}")
+    if order_check:
+        base_args.append("--order-check")
 
     args = " ".join(base_args)
 
@@ -257,13 +260,33 @@ def _check_gro_stats(cfg, test_queue, stats_before,
                      expect_wire=gro_coalesced * 2)

+@ksft_variants([4, 32, 512])
+def test_gro_order(cfg, num_flows):
+    """
+    Test that HW GRO preserves packet ordering between flows.
+
+    Packets may get delayed until the aggreate is released,
+    but reordering between aggregates and packet terminating
+    the aggregate and normal packets should not happen.
+
+    Note that this test is stricter than truly required.
+    Reordering packets between flows should not cause issues.
+    This test will also fail if traffic is run over an ECMP fabric.
+    """
+    _setup_hw_gro(cfg)
+    _setup_isolated_queue(cfg)
+
+    _run_gro_test(cfg, "capacity", num_flows=num_flows, order_check=True)
+
+
 def main() -> None:
     """ Ksft boiler plate main """
 
     with NetDrvEpEnv(__file__, nsim_test=False) as cfg:
         cfg.netnl = NetdevFamily()
         ksft_run([test_gro_stats_single,
-                  test_gro_stats_full], args=(cfg,))
+                  test_gro_stats_full,
+                  test_gro_order], args=(cfg,))
     ksft_exit()

-- 
2.53.0