Allow specifying bridge port STP state by name rather than number.

The existing behaviour forces one to memorize the integer constants for
STP port states.

    # bridge link set dev dummy0 state 3

This patch makes it possible to use the lowercased port state name.

    # bridge link set dev dummy0 state forwarding

Invalid non-integer inputs now cause exit with status -1.
Signed-off-by: Alex Pilon <alp@alexpilon.ca>

bridge/link.c

@@ -316,7 +316,19 @@ static int brlink_modify(int argc, char **argv)
 			priority = atoi(*argv);
 		} else if (strcmp(*argv, "state") == 0) {
 			NEXT_ARG();
-			state = atoi(*argv);
+			char *endptr;
+			size_t nstates = sizeof(port_states) / sizeof(*port_states);
+			state = strtol(*argv, &endptr, 10);
+			if (!(**argv != '\0' && *endptr == '\0')) {
+				for (state = 0; state < nstates; state++)
+					if (strcmp(port_states[state], *argv) == 0)
+						break;
+				if (state == nstates) {
+					fprintf(stderr,
+						"Error: invalid STP port state\n");
+					exit(-1);
+				}
+			}
 		} else if (strcmp(*argv, "hwmode") == 0) {
 			NEXT_ARG();
 			flags = BRIDGE_FLAGS_SELF;

man/man8/bridge.8

@@ -207,7 +207,9 @@ droot port selectio algorithms.
 .TP
 .BI state " STATE "
 the operation state of the port.  This is primarily used by user space STP/RSTP
-implementation.  The following is a list of valid values:
+implementation.  One may enter a lowercased port state name, or one of the
+numbers below.  Negative inputs are ignored, and unrecognized names return an
+error.
 
 .B 0
 - port is DISABLED.  Make this port completely inactive.