selftests: net: fix timestamp not arriving in cmsg_time.sh

On slow machines the SND timestamp sometimes doesn't arrive before
we quit. The test only waits as long as the packet delay, so it's
easy for a race condition to happen.

Double the wait but do a bit of polling, once the SND timestamp
arrives there's no point to wait any longer.

This fixes the "TXTIME abs" failures on debug kernels, like:

   Case ICMPv4  - TXTIME abs returned '', expected 'OK'

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240510005705.43069-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/testing/selftests/net/cmsg_sender.c b/tools/testing/selftests/net/cmsg_sender.c
index c79e65581dc379ecddcc7177b7a6406c68b6c551..161db24e3c409fe3129247f183c54a82558e7d28 100644 (file)
--- a/tools/testing/selftests/net/cmsg_sender.c
+++ b/tools/testing/selftests/net/cmsg_sender.c
@@ -333,16 +333,17 @@ static const char *cs_ts_info2str(unsigned int info)
        return "unknown";
 }
 
-static void
+static unsigned long
 cs_read_cmsg(int fd, struct msghdr *msg, char *cbuf, size_t cbuf_sz)
 {
        struct sock_extended_err *see;
        struct scm_timestamping *ts;
+       unsigned long ts_seen = 0;
        struct cmsghdr *cmsg;
        int i, err;
 
        if (!opt.ts.ena)
-               return;
+               return 0;
        msg->msg_control = cbuf;
        msg->msg_controllen = cbuf_sz;
 
@@ -396,8 +397,11 @@ cs_read_cmsg(int fd, struct msghdr *msg, char *cbuf, size_t cbuf_sz)
                        printf(" %5s ts%d %lluus\n",
                               cs_ts_info2str(see->ee_info),
                               i, rel_time);
+                       ts_seen |= 1 << see->ee_info;
                }
        }
+
+       return ts_seen;
 }
 
 static void ca_set_sockopts(int fd)
@@ -509,10 +513,16 @@ int main(int argc, char *argv[])
        err = ERN_SUCCESS;
 
        if (opt.ts.ena) {
-               /* Make sure all timestamps have time to loop back */
-               usleep(opt.txtime.delay);
+               unsigned long seen;
+               int i;
 
-               cs_read_cmsg(fd, &msg, cbuf, sizeof(cbuf));
+               /* Make sure all timestamps have time to loop back */
+               for (i = 0; i < 40; i++) {
+                       seen = cs_read_cmsg(fd, &msg, cbuf, sizeof(cbuf));
+                       if (seen & (1 << SCM_TSTAMP_SND))
+                               break;
+                       usleep(opt.txtime.delay / 20);
+               }
        }
 
 err_out: