check for known-slave in sentinel rewrite config (#11775)

Fix the following config file error

```
*** FATAL CONFIG FILE ERROR (Redis 6.2.7) ***
Reading the configuration file, at line 152
>>> 'sentinel known-replica XXXX 127.0.0.1 5001'
Duplicate hostname and port for replica.
```


that is happening when a user uses the legacy key "known-slave" in
the config file and a config rewrite occurs. The config rewrite logic won't
replace the old  line "sentinel known-slave XXXX 127.0.0.1 5001" and
would add a new line with "sentinel known-replica XXXX 127.0.0.1 5001"
which results in the error above "Duplicate hostname and port for replica."

example:

Current sentinal.conf
```
...

sentinel known-slave XXXX 127.0.0.1 5001
sentinel example-random-option X
...
```
after the config rewrite logic runs:
```
....
sentinel known-slave XXXX 127.0.0.1 5001
sentinel example-random-option X

# Generated by CONFIG REWRITE
sentinel known-replica XXXX 127.0.0.1 5001
```

This bug only exists in Redis versions >=6.2 because prior to that it was hidden
by the effects of this bug https://github.com/redis/redis/issues/5388 that was fixed
in https://github.com/redis/redis/pull/8271 and was released in versions >=6.2

3 files changed, 10 insertions, 4 deletions

diff --git a/src/config.c b/src/config.c
index 94fc039e2..9a3f8d969 100644
--- a/src/config.c
+++ b/src/config.c
@@ -1221,7 +1221,7 @@ struct rewriteConfigState *rewriteConfigReadOldFile(char *path) {
  *
  * "line" is either used, or freed, so the caller does not need to free it
  * in any way. */
-void rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *option, sds line, int force) {
+int rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *option, sds line, int force) {
     sds o = sdsnew(option);
     list *l = dictFetchValue(state->option_to_line,o);
 
@@ -1231,7 +1231,7 @@ void rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *opti
         /* Option not used previously, and we are not forced to use it. */
         sdsfree(line);
         sdsfree(o);
-        return;
+        return 0;
     }
 
     if (l) {
@@ -1254,6 +1254,7 @@ void rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *opti
         rewriteConfigAppendLine(state,line);
     }
     sdsfree(o);
+    return 1;
 }
 
 /* Write the long long 'bytes' value as a string in a way that is parsable
diff --git a/src/sentinel.c b/src/sentinel.c
index b4dead7de..03482fdd2 100644
--- a/src/sentinel.c
+++ b/src/sentinel.c
@@ -2176,7 +2176,12 @@ void rewriteConfigSentinelOption(struct rewriteConfigState *state) {
             line = sdscatprintf(sdsempty(),
                 "sentinel known-replica %s %s %d",
                 master->name, announceSentinelAddr(slave_addr), slave_addr->port);
-            rewriteConfigRewriteLine(state,"sentinel known-replica",line,1);
+            /* try to replace any known-slave option first if found */
+            if (rewriteConfigRewriteLine(state, "sentinel known-slave", sdsdup(line), 0) == 0) {
+                rewriteConfigRewriteLine(state, "sentinel known-replica", line, 1);
+            } else {
+                sdsfree(line);
+            }
             /* rewriteConfigMarkAsProcessed is handled after the loop */
         }
         dictReleaseIterator(di2);
diff --git a/src/server.h b/src/server.h
index dd50e9089..02ec91ee0 100644
--- a/src/server.h
+++ b/src/server.h
@@ -3171,7 +3171,7 @@ void loadServerConfig(char *filename, char config_from_stdin, char *options);
 void appendServerSaveParams(time_t seconds, int changes);
 void resetServerSaveParams(void);
 struct rewriteConfigState; /* Forward declaration to export API. */
-void rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *option, sds line, int force);
+int rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *option, sds line, int force);
 void rewriteConfigMarkAsProcessed(struct rewriteConfigState *state, const char *option);
 int rewriteConfig(char *path, int force_write);
 void initConfigValues();