On 2/16/25 7:42 PM, Jason Xing wrote:
Add TCP_RTO_MAX_MS selftests for active and passive flows
in various bpf callbacks. Even though the TCP_RTO_MAX_MS
can be used in established phase, we highly discourage
to do so because it may trigger unexpected behaviour.
On the contrary, it's highly recommended that the maximum
value of RTO is set before first time of transmission, such
as BPF_SOCK_OPS_{PASSIVE|ACTIVE}_ESTABLISHED_CB,
s/,/./
What unexpected behavior when setting in BPF after the established state?
Setting it after the established state or not is not specific to BPF. syscall
can choose to do it after the connection established also. The above makes it
unclear what unexpected behavior that the BPF prog will cause if TCP_RTO_MAX_MS
is used in BPF instead of syscall.
If there is subtle difference between calling TCP_RTO_MAX_MS from bpf and from
syscall, please write it clearly what are the unexpected behaviors when calling
in BPF after the established states.
Otherwise, the commit message can be just this:
Test the TCP_RTO_MAX_MS optname in the existing setget_sockopt test.
Signed-off-by: Jason Xing <kerneljasonxing@xxxxxxxxx>
---
tools/include/uapi/linux/tcp.h | 1 +
tools/testing/selftests/bpf/progs/bpf_tracing_net.h | 1 +
tools/testing/selftests/bpf/progs/setget_sockopt.c | 1 +
3 files changed, 3 insertions(+)
diff --git a/tools/include/uapi/linux/tcp.h b/tools/include/uapi/linux/tcp.h
index 13ceeb395eb8..7989e3f34a58 100644
--- a/tools/include/uapi/linux/tcp.h
+++ b/tools/include/uapi/linux/tcp.h
@@ -128,6 +128,7 @@ enum {
#define TCP_CM_INQ TCP_INQ
#define TCP_TX_DELAY 37 /* delay outgoing packets by XX usec */
+#define TCP_RTO_MAX_MS 44 /* max rto time in ms */
Have you checked if this change is really needed?
#define TCP_REPAIR_ON 1
diff --git a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
index 59843b430f76..eb6ed1b7b2ef 100644
--- a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
+++ b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
@@ -49,6 +49,7 @@
#define TCP_SAVED_SYN 28
#define TCP_CA_NAME_MAX 16
#define TCP_NAGLE_OFF 1
+#define TCP_RTO_MAX_MS 44
#define TCP_ECN_OK 1
#define TCP_ECN_QUEUE_CWR 2
diff --git a/tools/testing/selftests/bpf/progs/setget_sockopt.c b/tools/testing/selftests/bpf/progs/setget_sockopt.c
index 6dd4318debbf..106fe430f41b 100644
--- a/tools/testing/selftests/bpf/progs/setget_sockopt.c
+++ b/tools/testing/selftests/bpf/progs/setget_sockopt.c
@@ -61,6 +61,7 @@ static const struct sockopt_test sol_tcp_tests[] = {
{ .opt = TCP_NOTSENT_LOWAT, .new = 1314, .expected = 1314, },
{ .opt = TCP_BPF_SOCK_OPS_CB_FLAGS, .new = BPF_SOCK_OPS_ALL_CB_FLAGS,
.expected = BPF_SOCK_OPS_ALL_CB_FLAGS, },
+ { .opt = TCP_RTO_MAX_MS, .new = 2000, .expected = 2000, },
{ .opt = 0, },
};
