agetty: Reprompt and reprint /etc/issue when asked

Add an 'agetty --reload' command which asks all running agetty
commands to display their prompts again.

Several of the /etc/issue escape codes such as \4 and \S depend on
variable data which can change after the agetty prompt is displayed.
This can cause stale data to be displayed when a user looks at a VT,
especially in cases of DHCP racing with system start up.

We never want this to occur once the user has started typing a
user name. So we detect when the user starts typing, after which
no further reprompting occurs after that point.

[kzak@redhat.com: - add #ifdefs to make it usable on non-inotify systems,
                  - use futimens() with NULL timespec
                  - add --reaload to usage()]

Signed-off-by: Stef Walter <stefw-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/configure.ac b/configure.ac
index 02fc411f7d7ee3c0e8356bff71332ccee812c88f..c6c74da029e071bb091125dbeeb991ce270475ce 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -303,6 +303,7 @@ AC_CHECK_FUNCS([ \
        getmntinfo \
        getrlimit \
        inotify_init \
+       inotify_init1 \
        jrand48 \
        lchown \
        llseek \

diff --git a/term-utils/agetty.8 b/term-utils/agetty.8
index 27a0d1b8670863f54c8c37c34e9ae57b3a5fc166..4ef1e6b8c1ff7c40549834d52dc2081b64b0a22b 100644 (file)
--- a/term-utils/agetty.8
+++ b/term-utils/agetty.8
@@ -252,6 +252,12 @@ Sleep seconds before open tty.
 \-\-nice \fInumber\fP
 Run login with this priority.
 .TP
+\-\-reload
+Ask all running agetty instances to reload and update their displayed prompts,
+if the user has not yet commenced logging in. After doing so the command will
+exit. This feature might be unnsupported on systems without Linux
+.BR inotify (7).
+.TP
 \-\-version
 Display version information and exit.
 .TP

diff --git a/term-utils/agetty.c b/term-utils/agetty.c
index 2b5932d60de85339ece9c70bbefc6a0beabcd9ed..5d32cc1a270642c9080dd49378bb9281029a45a6 100644 (file)
--- a/term-utils/agetty.c
+++ b/term-utils/agetty.c
@@ -112,6 +112,22 @@
 #define LOGIN          "login: "
 #define LOGIN_ARGV_MAX 16              /* Numbers of args for login */
 
+/*
+ * agetty --reload
+ */
+#define AGETTY_RELOAD                  /* enabled by default */
+
+#ifndef HAVE_INOTIFY_INIT1
+# undef AGETTY_RELOAD                  /* disable on systems without inotify */
+#endif
+
+#ifdef AGETTY_RELOAD
+# include <sys/inotify.h>
+# define AGETTY_RELOAD_FILENAME "/run/agetty.reload"   /* trigger file */
+# define AGETTY_RELOAD_FDNONE  -2                      /* uninitialized fd */
+static int inotify_fd = AGETTY_RELOAD_FDNONE;
+#endif
+
 /*
  * When multiple baud rates are specified on the command line, the first one
  * we will try is the first one specified.
@@ -281,6 +297,7 @@ static ssize_t append(char *dest, size_t len, const char  *sep, const char *src)
 static void check_username (const char* nm);
 static void login_options_to_argv(char *argv[], int *argc, char *str, char *username);
 static int plymouth_command(const char* arg);
+static void reload_agettys(void);
 
 /* Fake hostname for ut_host specified on command line. */
 static char *fakehost;
@@ -587,6 +604,7 @@ static void parse_args(int argc, char **argv, struct options *op)
                HELP_OPTION,
                ERASE_CHARS_OPTION,
                KILL_CHARS_OPTION,
+               RELOAD_OPTION,
        };
        const struct option longopts[] = {
                {  "8bits",          no_argument,        0,  '8'  },
@@ -618,6 +636,7 @@ static void parse_args(int argc, char **argv, struct options *op)
                {  "nohints",        no_argument,        0,  NOHINTS_OPTION },
                {  "nohostname",     no_argument,        0,  NOHOSTNAME_OPTION },
                {  "long-hostname",  no_argument,        0,  LONGHOSTNAME_OPTION },
+               {  "reload",         no_argument,        0,  RELOAD_OPTION },
                {  "version",        no_argument,        0,  VERSION_OPTION  },
                {  "help",           no_argument,        0,  HELP_OPTION     },
                {  "erase-chars",    required_argument,  0,  ERASE_CHARS_OPTION },
@@ -736,6 +755,9 @@ static void parse_args(int argc, char **argv, struct options *op)
                case KILL_CHARS_OPTION:
                        op->killchars = optarg;
                        break;
+               case RELOAD_OPTION:
+                       reload_agettys();
+                       exit(EXIT_SUCCESS);
                case VERSION_OPTION:
                        printf(_("%s from %s\n"), program_invocation_short_name,
                               PACKAGE_STRING);
@@ -1113,6 +1135,21 @@ static void open_tty(char *tty, struct termios *tp, struct options *op)
        setenv("TERM", op->term, 1);
 }
 
+/* Initialize termios settings. */
+static void termio_clear(int fd)
+{
+       /*
+        * Do not write a full reset (ESC c) because this destroys
+        * the unicode mode again if the terminal was in unicode
+        * mode.  Also it clears the CONSOLE_MAGIC features which
+        * are required for some languages/console-fonts.
+        * Just put the cursor to the home position (ESC [ H),
+        * erase everything below the cursor (ESC [ J), and set the
+        * scrolling region to the full window (ESC [ r)
+        */
+       write_all(fd, "\033[r\033[H\033[J", 9);
+}
+
 /* Initialize termios settings. */
 static void termio_init(struct options *op, struct termios *tp)
 {
@@ -1166,18 +1203,8 @@ static void termio_init(struct options *op, struct termios *tp)
                if ((tp->c_cflag & (CS8|PARODD|PARENB)) == CS8)
                        op->flags |= F_EIGHTBITS;
 
-               if ((op->flags & F_NOCLEAR) == 0) {
-                       /*
-                        * Do not write a full reset (ESC c) because this destroys
-                        * the unicode mode again if the terminal was in unicode
-                        * mode.  Also it clears the CONSOLE_MAGIC features which
-                        * are required for some languages/console-fonts.
-                        * Just put the cursor to the home position (ESC [ H),
-                        * erase everything below the cursor (ESC [ J), and set the
-                        * scrolling region to the full window (ESC [ r)
-                        */
-                       write_all(STDOUT_FILENO, "\033[r\033[H\033[J", 9);
-               }
+               if ((op->flags & F_NOCLEAR) == 0)
+                       termio_clear(STDOUT_FILENO);
                return;
        }
 
@@ -1593,6 +1620,70 @@ static void next_speed(struct options *op, struct termios *tp)
        tcsetattr(STDIN_FILENO, TCSANOW, tp);
 }
 
+#ifdef AGETTY_RELOAD
+static int wait_for_term_input(int fd)
+{
+       char buffer[sizeof(struct inotify_event) + NAME_MAX + 1];
+       struct termios orig, nonc;
+       fd_set rfds;
+       int count, i;
+
+       /* Our aim here is to fall through if something fails
+         * and not be stuck waiting. On failure assume we have input */
+
+       if (tcgetattr(fd, &orig) != 0)
+               return 1;
+
+       memcpy(&nonc, &orig, sizeof (nonc));
+       nonc.c_lflag &= ~(ICANON | ECHO | ECHOE | ECHOK | ECHOKE);
+       nonc.c_cc[VMIN] = 1;
+       nonc.c_cc[VTIME] = 0;
+
+       if (tcsetattr(fd, TCSANOW, &nonc) != 0)
+               return 1;
+
+       if (inotify_fd == AGETTY_RELOAD_FDNONE) {
+               /* initialize reload trigger inotify stuff */
+               inotify_fd = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
+               if (inotify_fd > 0)
+                       inotify_add_watch(inotify_fd, AGETTY_RELOAD_FILENAME,
+                                         IN_ATTRIB | IN_MODIFY);
+       }
+
+       FD_ZERO(&rfds);
+       FD_SET(fd, &rfds);
+
+       if (inotify_fd >= 0)
+               FD_SET(inotify_fd, &rfds);
+
+       /* If waiting fails, just fall through, presumably reading input will fail */
+       if (select(max(fd, inotify_fd) + 1, &rfds, NULL, NULL, NULL) < 0)
+               return 1;
+
+       if (FD_ISSET(fd, &rfds)) {
+               count = read(fd, buffer, sizeof (buffer));
+
+               tcsetattr(fd, TCSANOW, &orig);
+
+               /* Reinject the bytes we read back into the buffer, usually just one byte */
+               for (i = 0; i < count; i++)
+                       ioctl(fd, TIOCSTI, buffer + i);
+
+               /* Have terminal input */
+               return 1;
+
+       } else {
+               tcsetattr(fd, TCSANOW, &orig);
+
+               /* Just drain the inotify buffer */
+               while (read(inotify_fd, buffer, sizeof (buffer)) > 0);
+
+               /* Need to reprompt */
+               return 0;
+       }
+}
+#endif  /* AGETTY_RELOAD */
+
 /* Get user name, establish parity, speed, erase, kill & eol. */
 static char *get_logname(struct options *op, struct termios *tp, struct chardata *cp)
 {
@@ -1628,6 +1719,14 @@ static char *get_logname(struct options *op, struct termios *tp, struct chardata
                /* Write issue file and prompt */
                do_prompt(op, tp);
 
+#ifdef AGETTY_RELOAD
+               /* If asked to reprompt *before* terminal input arrives, then do so */
+               if (!wait_for_term_input(STDIN_FILENO)) {
+                       if (op->flags & F_VCONSOLE)
+                               termio_clear(STDOUT_FILENO);
+                       continue;
+               }
+#endif
                cp->eol = '\0';
 
                /* Read name, watch for break and end-of-line. */
@@ -1895,6 +1994,7 @@ static void __attribute__ ((__noreturn__)) usage(FILE *out)
        fputs(_("     --chdir <directory>    chdir before the login\n"), out);
        fputs(_("     --delay <number>       sleep seconds before prompt\n"), out);
        fputs(_("     --nice <number>        run login with this priority\n"), out);
+       fputs(_("     --reload               reload prompts on running agetty instances\n"), out);
        fputs(_("     --help                 display this help and exit\n"), out);
        fputs(_("     --version              output version information and exit\n"), out);
        fprintf(out, USAGE_MAN_TAIL("agetty(8)"));
@@ -2364,3 +2464,20 @@ static int plymouth_command(const char* arg)
        }
        return 1;
 }
+
+static void reload_agettys(void)
+{
+#ifdef AGETTY_RELOAD
+       int fd = open(AGETTY_RELOAD_FILENAME, O_CREAT|O_CLOEXEC|O_WRONLY, 0700);
+
+       if (fd < 0)
+               err(EXIT_FAILURE, _("cannot open: %s"), AGETTY_RELOAD_FILENAME);
+
+       if (futimes(fd, NULL) < 0 || close(fd) < 0)
+               err(EXIT_FAILURE, _("cannot touch file: %s"),
+                   AGETTY_RELOAD_FILENAME);
+#else
+       /* very unusual */
+       errx(EXIT_FAILURE, _("--reload unssupported on your system."));
+#endif
+}