canutils/slcan: explicitly manage the interface.

A recent change (apache/nuttx#16199) has made the bitrate setting no
longer bring the interface up. Moreover, it is now no longer possible to change bitrate
of a CAN interface if it is up. Therefore, slcan needs to bring the interface down
to change it. Fortunately, it already had commands to open and close the interface
which map nicely to this.

Signed-off-by: Carlos Sanchez <carlossanchez@geotab.com>

Author: csanchezdll

canutils/slcan/slcan.c

@@ -316,9 +316,22 @@ int main(int argc, char *argv[])
                         {
                           /* open CAN interface */
 
-                          mode = 1;
-                          debug_print("Open interface\n");
-                          ok_return(fd);
+                          struct ifreq ifr;
+
+                          strlcpy(ifr.ifr_name, argv[1], IFNAMSIZ);
+
+                          ifr.ifr_flags = IFF_UP;
+                          if (ioctl(s, SIOCSIFFLAGS, &ifr) < 0)
+                            {
+                              syslog(LOG_ERR, "Open interface failed\n");
+                              fail_return(fd);
+                            }
+                          else
+                            {
+                              mode = 1;
+                              debug_print("Open interface\n");
+                              ok_return(fd);
+                            }
                         }
                       else if (buf[0] == 'S')
                         {
@@ -392,9 +405,22 @@ int main(int argc, char *argv[])
                         {
                           /* close interface */
 
-                          mode = 0;
-                          debug_print("Close interface\n");
-                          ok_return(fd);
+                          struct ifreq ifr;
+
+                          strlcpy(ifr.ifr_name, argv[1], IFNAMSIZ);
+
+                          ifr.ifr_flags = 0;
+                          if (ioctl(s, SIOCSIFFLAGS, &ifr) < 0)
+                            {
+                              syslog(LOG_ERR, "Close interface failed\n");
+                              fail_return(fd);
+                            }
+                          else
+                            {
+                              mode = 0;
+                              debug_print("Close interface\n");
+                              ok_return(fd);
+                            }
                         }
                       else if (buf[0] == 'T')
                         {