selftests/net: big_tcp: return xfail on slow machines

After debugging the following output for big_tcp.sh on a board:

CLI GSO | GW GRO | GW GSO | SER GRO

on        on       on       on      : [PASS]
on        off      on       off     : [PASS]
off       on       on       on      : [FAIL_on_link1]
on        on       off      on      : [FAIL_on_link1]

Davide Caratti found that by default the test duration 1s is too short in slow systems to reach the correct cwd size necessary for tcp/ip to generate at least one packet bigger than 65536 (matching the iptables match on length rule the test evaluates)

This skips (with xfail) the aforementioned failing combinations when KSFT_MACHINE_SLOW is set. For that the test has been modified to use facilities from net/lib.sh.

The new output for the test will look like this (example with a forced XFAIL)

Testing for BIG TCP:
CLI GSO | GW GRO | GW GSO | SER GRO
TEST: on on on on [ OK ]
TEST: on off on off [ OK ]
TEST: off on on on [XFAIL]

---
Changes in v3:
- Added 12 characters of length to the Fixes: tag
- Exit test on the first fail

Changes in v2:
- Don't break the loop and use lib.sh facilities (thanks Peter Machata)
- Rephrased the subject from "longer netperf session on slow machines"
as the patch is not configuring a longer session but skipping
- Added tags and SOB and the Fixes: hash (thank you Davide Caratti)
- Link to v1: https://lore.kernel.org/all/b800a71479a24a4142542051636e980c3b547434.1739794830.git.pablmart@redhat.com/

---
 tools/testing/selftests/net/big_tcp.sh | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

index 2db9d15cd45f..52b9a76b1c19 100755
@@ -21,8 +21,7 @@ CLIENT_GW6="2001:db8:1::2"
 MAX_SIZE=128000
 CHK_SIZE=65535
 
-# Kselftest framework requirement - SKIP code is 4.
-ksft_skip=4
+source lib.sh
 
 setup() {
 	ip netns add $CLIENT_NS

@@ -143,21 +142,20 @@ do_test() {
 	start_counter link3 $SERVER_NS
 	do_netperf $CLIENT_NS
 
-	if check_counter link1 $ROUTER_NS; then
-		check_counter link3 $SERVER_NS || ret="FAIL_on_link3"
-	else
-		ret="FAIL_on_link1"
-	fi
+	check_counter link1 $ROUTER_NS
+	check_err $? "fail on link1"
+	check_counter link3 $SERVER_NS
+	check_err $? "fail on link3"
 
 	stop_counter link1 $ROUTER_NS
 	stop_counter link3 $SERVER_NS
-	printf "%-9s %-8s %-8s %-8s: [%s]\n" \
-		$cli_tso $gw_gro $gw_tso $ser_gro $ret
-	test $ret = "PASS"
+	log_test "$(printf "%-9s %-8s %-8s %-8s" \
+			$cli_tso $gw_gro $gw_tso $ser_gro)"
+	test $RET -eq 0
 }
 
 testup() {
-	echo "CLI GSO | GW GRO | GW GSO | SER GRO" && \
+	echo "      CLI GSO | GW GRO | GW GSO | SER GRO" && \
 	do_test "on"  "on"  "on"  "on"  && \
 	do_test "on"  "off" "on"  "off" && \
 	do_test "off" "on"  "on"  "on"  && \

@@ -176,7 +174,8 @@ if ! ip link help 2>&1 | grep gso_ipv4_max_size &> /dev/null; then
 fi
 
 trap cleanup EXIT
+xfail_on_slow
 setup && echo "Testing for BIG TCP:" && \
 NF=4 testup && echo "***v4 Tests Done***" && \
 NF=6 testup && echo "***v6 Tests Done***"
-exit $?
+exit $EXIT_STATUS

2.48.1