agetty: allow full control on CLOCAL flag

Now the -L option allows to explicitly enable CLOCAL flag.

Unfortunately sometimes it's necessary to clear the flag. This patch
add optional argument =<mode> to specify 'auto', 'always' and 'never'
to control CLOCAL flag.

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=816342
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/term-utils/agetty.8 b/term-utils/agetty.8
index 64a1dd2896f2030e8e991f27c2ba8bd342af8df3..8d5286c58c54d573f7964590433bcc9208f82e5c 100644 (file)
--- a/term-utils/agetty.8
+++ b/term-utils/agetty.8
@@ -138,10 +138,20 @@ This allows the use of a non-standard login program (for example,
 one that asks for a dial-up password or that uses a different
 password file).
 .TP
-\-L, \-\-local\-line
-Force the line to be a local line with no need for carrier detect. This can
+\-L, \-\-local\-line [=\fImode\fP]
+Control CLOCAL line flag, the optional argument \fImode\fP is 'auto', 'always' or 'never'.
+If the \fImode\fP argument is omitted then the default is 'always'. If the
+\-\-local\-line option is ommitted at all then the default is 'auto'.
+
+The \fImode\fP 'always' forces the line to be a local line with no need for carrier detect. This can
 be useful when you have a locally attached terminal where the serial line
 does not set the carrier detect signal.
+
+The \fImode\fP 'never' explicitly clears CLOCAL flags from line setting and
+the carrier detect signal is expected on the line.
+
+The \fImode\fP 'auto' (agetty default) does not modify CLOCAL setting
+and follows the setting enabled by kernel.
 .TP
 \-m, \-\-extract\-baud
 Try to extract the baud rate the CONNECT status message

diff --git a/term-utils/agetty.c b/term-utils/agetty.c
index dd52f700ff69ebede6ca3a702d89a500ed94f4a5..0d01e7ec3c52aa222cb513a8b318b483f89f4b2f 100644 (file)
--- a/term-utils/agetty.c
+++ b/term-utils/agetty.c
@@ -132,13 +132,20 @@ struct options {
        int delay;                      /* Sleep seconds before prompt */
        int nice;                       /* Run login with this priority */
        int numspeed;                   /* number of baud rates to try */
+       int clocal;                     /* CLOCAL_MODE_* */
        speed_t speeds[MAX_SPEED];      /* baud rates to be tried */
 };
 
+enum {
+       CLOCAL_MODE_AUTO = 0,
+       CLOCAL_MODE_ALWAYS,
+       CLOCAL_MODE_NEVER
+};
+
 #define        F_PARSE         (1<<0)  /* process modem status messages */
 #define        F_ISSUE         (1<<1)  /* display /etc/issue */
 #define        F_RTSCTS        (1<<2)  /* enable RTS/CTS flow control */
-#define F_LOCAL                (1<<3)  /* force local */
+
 #define F_INITSTRING    (1<<4) /* initstring is set */
 #define F_WAITCRLF     (1<<5)  /* wait for CR or LF */
 #define F_CUSTISSUE    (1<<6)  /* give alternative issue file */
@@ -314,7 +321,8 @@ int main(int argc, char **argv)
                           strlen(options.initstring));
        }
 
-       if (!serial_tty_option(&options, F_LOCAL))
+       if ((options.flags & F_VCONSOLE) == 0 &&
+           options.clocal == CLOCAL_MODE_ALWAYS)
                /* Go to blocking write mode unless -L is specified. */
                fcntl(STDOUT_FILENO, F_SETFL,
                      fcntl(STDOUT_FILENO, F_GETFL, 0) & ~O_NONBLOCK);
@@ -541,7 +549,7 @@ static void parse_args(int argc, char **argv, struct options *op)
                {  "init-string",    required_argument,  0,  'I'  },
                {  "noclear",        no_argument,        0,  'J'  },
                {  "login-program",  required_argument,  0,  'l'  },
-               {  "local-line",     no_argument,        0,  'L'  },
+               {  "local-line",     optional_argument,  0,  'L'  },
                {  "extract-baud",   no_argument,        0,  'm'  },
                {  "skip-login",     no_argument,        0,  'n'  },
                {  "nonewline",      no_argument,        0,  'N'  },
@@ -610,7 +618,18 @@ static void parse_args(int argc, char **argv, struct options *op)
                        op->login = optarg;
                        break;
                case 'L':
-                       op->flags |= F_LOCAL;
+                       /* -L and -L=always have the same meaning */
+                       op->clocal = CLOCAL_MODE_ALWAYS;
+                       if (optarg) {
+                               if (strcmp(optarg, "=always") == 0)
+                                       op->clocal = CLOCAL_MODE_ALWAYS;
+                               else if (strcmp(optarg, "=never") == 0)
+                                       op->clocal = CLOCAL_MODE_NEVER;
+                               else if (strcmp(optarg, "=auto") == 0)
+                                       op->clocal = CLOCAL_MODE_AUTO;
+                               else
+                                       log_err(_("unssuported --local-line mode argument"));
+                       }
                        break;
                case 'm':
                        op->flags |= F_PARSE;
@@ -1097,8 +1116,19 @@ static void termio_init(struct options *op, struct termios *tp)
        cfsetispeed(tp, ispeed);
        cfsetospeed(tp, ospeed);
 
-       if (op->flags & F_LOCAL)
-               tp->c_cflag |= CLOCAL;
+       /* The default is to follow setting from kernel, but it's possible
+        * to explicitly remove/add CLOCAL flag by -L[=<mode>]*/
+       switch (op->clocal) {
+       case CLOCAL_MODE_ALWAYS:
+               tp->c_cflag |= CLOCAL;          /* -L or -L=always */
+               break;
+       case CLOCAL_MODE_NEVER:
+               tp->c_cflag &= ~CLOCAL;         /* -L=never */
+               break;
+       case CLOCAL_MODE_AUTO:                  /* -L=auto */
+               break;
+       }
+
 #ifdef HAVE_STRUCT_TERMIOS_C_LINE
        tp->c_line = 0;
 #endif
@@ -1655,7 +1685,7 @@ static void __attribute__ ((__noreturn__)) usage(FILE *out)
        fputs(_(" -i, --noissue              do not display issue file\n"), out);
        fputs(_(" -I, --init-string <string> set init string\n"), out);
        fputs(_(" -l, --login-program <file> specify login program\n"), out);
-       fputs(_(" -L, --local-line           force local line\n"), out);
+       fputs(_(" -L, --local-line[=<mode>]  cotrol local line flag\n"), out);
        fputs(_(" -m, --extract-baud         extract baud rate during connect\n"), out);
        fputs(_(" -n, --skip-login           do not prompt for login\n"), out);
        fputs(_(" -o, --login-options <opts> options that are passed to login\n"), out);