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agetty: Reload only if it is really needed 

If netlink event arrives and related escapes are part of issue, agetty
reloads and re-display the prompt. Reload is triggered not only by IP
address change, but also by IPv6 RAs. In some environments it causes
reload several times in a minute, and even complicates the login.

To prevent this, reload only if a real change appears.

This consists of:
split print_issue_file() to several functions:

eval_issue_file() prints issue to memory. It does not affect terminal in
any way.

print_issue_file() prints issue file from memory.

cmp_issue_file() compares the issue file and returns true, if reload is
needed.

The implementation requires additional change:

do_prompt() does not evaluate the issue file. It is responsibility of
calling function.

Test suite:

Use issue that contais \4 and/or \6 escape.

After installing new instance, restart agetty by typing a letter and then
Enter 6 times.

To check whether reload happens, type a letter. When reload happens,
letter disappears.

1. Unplug network cable. Wait a while and re-plug network cable.
You should see 2 reloads on single stack and 3 reloads on dual stack.

2. Run a loop
while : ; do
	sed -i '$areload_test' /etc/issue
	agetty --reload
	sleep 3
	sed -i '/reload_test/d' /etc/issue
	agetty --reload
	sleep 3
done
You should see regular reload every 3 seconds.

3. Run a loop
while : ; do
	agetty --reload
	sleep 3
done
Before: You see regular reload every 3 seconds.
After: No reloads.

4. Run a loop
while : ; do
	ifconfig lo 127.0.0.1 netmask 255.0.0.0
	sleep 3
	ifconfig lo 127.0.0.2 netmask 255.0.0.0
	sleep 3
done
Before: You see regular reload every 3 seconds.
After: No reloads.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
This commit is contained in:
Stanislav Brabec 2018-10-10 19:26:34 +02:00 committed by Karel Zak
parent 36c55a8987
commit 6522d88d08
1 changed files with 100 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

141
term-utils/agetty.c
View File

@ -28,6 +28,7 @@
#include <utmpx.h>
#include <getopt.h>
#include <time.h>
#include <stdbool.h>
#include <sys/socket.h>
#include <langinfo.h>
#include <grp.h>
@ -328,6 +329,7 @@ static void check_username (const char* nm);
static void login_options_to_argv(char *argv[], int *argc, char *str, char *username);
static void reload_agettys(void);
static void print_issue_file(struct options *op, struct termios *tp);
static void eval_issue_file(struct options *op, struct termios *tp);
/* Fake hostname for ut_host specified on command line. */
static char *fakehost;
@ -463,10 +465,12 @@ int main(int argc, char **argv)
}
if (options.flags & F_NOPROMPT) { /* --skip-login */
eval_issue_file(&options, &termios);
print_issue_file(&options, &termios);
} else { /* regular (auto)login */
if (options.autolog) {
/* Autologin prompt */
eval_issue_file(&options, &termios);
do_prompt(&options, &termios);
printf(_("%s%s (automatic login)\n"), LOGIN, options.autolog);
} else {
@ -1730,9 +1734,66 @@ static void print_issue_file(struct options *op, struct termios *tp __attribute_
write_all(STDOUT_FILENO, "\r\n", 2);
}
}
static void eval_issue_file(struct options *op __attribute__((__unused__)), struct termios *tp __attribute__((__unused__)))
{
}
#else /* ISSUE_SUPPORT */
static FILE *issue_f;
static char *issue_mem = NULL;
static size_t issue_mem_sz;
static bool do_tcsetattr;
static bool do_tcrestore;
#ifdef AGETTY_RELOAD
static char *issue_mem_old = NULL;
#endif
static bool cmp_issue_file(void) {
if (issue_mem_old && issue_mem) {
if (!strcmp(issue_mem_old, issue_mem)) {
free(issue_mem_old);
issue_mem_old = issue_mem;
issue_mem = NULL;
return false;
}
} else
return true;
return true;
}
static void print_issue_file(struct options *op, struct termios *tp)
{
int oflag = tp->c_oflag; /* Save current setting. */
if ((op->flags & F_NONL) == 0) {
/* Issue not in use, start with a new line. */
write_all(STDOUT_FILENO, "\r\n", 2);
}
if (do_tcsetattr) {
if ((op->flags & F_VCONSOLE) == 0) {
/* Map new line in output to carriage return & new line. */
tp->c_oflag |= (ONLCR | OPOST);
tcsetattr(STDIN_FILENO, TCSADRAIN, tp);
}
}
write_all(STDOUT_FILENO, issue_mem, issue_mem_sz);
if (do_tcrestore) {
/* Restore settings. */
tp->c_oflag = oflag;
/* Wait till output is gone. */
tcsetattr(STDIN_FILENO, TCSADRAIN, tp);
}
#ifdef AGETTY_RELOAD
free(issue_mem_old);
issue_mem_old = issue_mem;
issue_mem = NULL;
#else
free(issue_mem);
issue_mem = NULL;
#endif
}
static void eval_issue_file(struct options *op, struct termios *tp)
{
const char *filename, *dirname = NULL;
FILE *f = NULL;
@ -1743,10 +1804,6 @@ static void print_issue_file(struct options *op, struct termios *tp)
#ifdef AGETTY_RELOAD
netlink_groups = 0;
#endif
if ((op->flags & F_NONL) == 0) {
/* Issue not in use, start with a new line. */
write_all(STDOUT_FILENO, "\r\n", 2);
}
if (!(op->flags & F_ISSUE))
return;
@ -1777,6 +1834,7 @@ static void print_issue_file(struct options *op, struct termios *tp)
dirname = _PATH_ISSUEDIR;
}
issue_f = open_memstream(&issue_mem, &issue_mem_sz);
#ifdef ISSUEDIR_SUPPORT
if (dirname) {
dd = open(dirname, O_RDONLY|O_CLOEXEC|O_DIRECTORY);
@ -1791,13 +1849,9 @@ static void print_issue_file(struct options *op, struct termios *tp)
f = fopen(filename, "r");
if (f || dirname) {
int c, oflag = tp->c_oflag; /* Save current setting. */
int c;
if ((op->flags & F_VCONSOLE) == 0) {
/* Map new line in output to carriage return & new line. */
tp->c_oflag |= (ONLCR | OPOST);
tcsetattr(STDIN_FILENO, TCSADRAIN, tp);
}
do_tcsetattr = true;
do {
#ifdef ISSUEDIR_SUPPORT
@ -1810,7 +1864,7 @@ static void print_issue_file(struct options *op, struct termios *tp)
if (c == '\\')
output_special_char(getc(f), op, tp, f);
else
putchar(c);
putc(c, issue_f);
}
fclose(f);
f = NULL;
@ -1818,12 +1872,8 @@ static void print_issue_file(struct options *op, struct termios *tp)
fflush(stdout);
if ((op->flags & F_VCONSOLE) == 0) {
/* Restore settings. */
tp->c_oflag = oflag;
/* Wait till output is gone. */
tcsetattr(STDIN_FILENO, TCSADRAIN, tp);
}
if ((op->flags & F_VCONSOLE) == 0)
do_tcrestore = true;
}
#ifdef ISSUEDIR_SUPPORT
@ -1837,6 +1887,7 @@ static void print_issue_file(struct options *op, struct termios *tp)
if (netlink_groups != 0)
open_netlink();
#endif
fclose(issue_f);
}
#endif /* ISSUE_SUPPORT */
@ -1851,11 +1902,14 @@ again:
if (op->flags & F_LOGINPAUSE) {
puts(_("[press ENTER to login]"));
#ifdef AGETTY_RELOAD
/* reload issue */
if (!wait_for_term_input(STDIN_FILENO)) {
/* reload issue */
if (op->flags & F_VCONSOLE)
termio_clear(STDOUT_FILENO);
goto again;
eval_issue_file(op, tp);
if (cmp_issue_file()) {
if (op->flags & F_VCONSOLE)
termio_clear(STDOUT_FILENO);
goto again;
}
}
#endif
getc(stdin);
@ -1976,17 +2030,22 @@ static char *get_logname(struct options *op, struct termios *tp, struct chardata
bp = logname;
*bp = '\0';
eval_issue_file(op, tp);
while (*logname == '\0') {
/* Write issue file and prompt */
do_prompt(op, tp);
#ifdef AGETTY_RELOAD
no_reload:
if (!wait_for_term_input(STDIN_FILENO)) {
/* refresh prompt -- discard input data, clear terminal
* and call do_prompt() again
*/
if ((op->flags & F_VCONSOLE) == 0)
sleep(1);
eval_issue_file(op, tp);
if (!cmp_issue_file())
goto no_reload;
tcflush(STDIN_FILENO, TCIFLUSH);
if (op->flags & F_VCONSOLE)
termio_clear(STDOUT_FILENO);
@ -2374,7 +2433,7 @@ static void print_addr(sa_family_t family, void *addr)
char buff[INET6_ADDRSTRLEN + 1];
inet_ntop(family, addr, buff, sizeof(buff));
printf("%s", buff);
fprintf(issue_f, "%s", buff);
}
/*
@ -2496,36 +2555,36 @@ static void output_special_char(unsigned char c, struct options *op,
if (get_escape_argument(fp, escname, sizeof(escname))) {
const char *esc = color_sequence_from_colorname(escname);
if (esc)
fputs(esc, stdout);
fputs(esc, issue_f);
} else
fputs("\033", stdout);
fputs("\033", issue_f);
break;
}
case 's':
uname(&uts);
printf("%s", uts.sysname);
fprintf(issue_f, "%s", uts.sysname);
break;
case 'n':
uname(&uts);
printf("%s", uts.nodename);
fprintf(issue_f, "%s", uts.nodename);
break;
case 'r':
uname(&uts);
printf("%s", uts.release);
fprintf(issue_f, "%s", uts.release);
break;
case 'v':
uname(&uts);
printf("%s", uts.version);
fprintf(issue_f, "%s", uts.version);
break;
case 'm':
uname(&uts);
printf("%s", uts.machine);
fprintf(issue_f, "%s", uts.machine);
break;
case 'o':
{
char *dom = xgetdomainname();
fputs(dom ? dom : "unknown_domain", stdout);
fputs(dom ? dom : "unknown_domain", issue_f);
free(dom);
break;
}
@ -2545,7 +2604,7 @@ static void output_special_char(unsigned char c, struct options *op,
(canon = strchr(info->ai_canonname, '.')))
dom = canon + 1;
}
fputs(dom ? dom : "unknown_domain", stdout);
fputs(dom ? dom : "unknown_domain", issue_f);
if (info)
freeaddrinfo(info);
free(host);
@ -2564,19 +2623,19 @@ static void output_special_char(unsigned char c, struct options *op,
break;
if (c == 'd') /* ISO 8601 */
printf("%s %s %d %d",
fprintf(issue_f, "%s %s %d %d",
nl_langinfo(ABDAY_1 + tm->tm_wday),
nl_langinfo(ABMON_1 + tm->tm_mon),
tm->tm_mday,
tm->tm_year < 70 ? tm->tm_year + 2000 :
tm->tm_year + 1900);
else
printf("%02d:%02d:%02d",
fprintf(issue_f, "%02d:%02d:%02d",
tm->tm_hour, tm->tm_min, tm->tm_sec);
break;
}
case 'l':
printf ("%s", op->tty);
fprintf (issue_f, "%s", op->tty);
break;
case 'b':
{
@ -2585,7 +2644,7 @@ static void output_special_char(unsigned char c, struct options *op,
for (i = 0; speedtab[i].speed; i++) {
if (speedtab[i].code == speed) {
printf("%ld", speedtab[i].speed);
fprintf(issue_f, "%ld", speedtab[i].speed);
break;
}
}
@ -2600,18 +2659,18 @@ static void output_special_char(unsigned char c, struct options *op,
var = read_os_release(op, varname);
if (var) {
if (strcmp(varname, "ANSI_COLOR") == 0)
printf("\033[%sm", var);
fprintf(issue_f, "\033[%sm", var);
else
fputs(var, stdout);
fputs(var, issue_f);
}
/* \S */
} else if ((var = read_os_release(op, "PRETTY_NAME"))) {
fputs(var, stdout);
fputs(var, issue_f);
/* \S and PRETTY_NAME not found */
} else {
uname(&uts);
fputs(uts.sysname, stdout);
fputs(uts.sysname, issue_f);
}
free(var);
@ -2629,9 +2688,9 @@ static void output_special_char(unsigned char c, struct options *op,
users++;
endutxent();
if (c == 'U')
printf(P_("%d user", "%d users", users), users);
fprintf(issue_f, P_("%d user", "%d users", users), users);
else
printf ("%d ", users);
fprintf (issue_f, "%d ", users);
break;
}
case '4':