syslogd: optional support for dropping dups. closes bug 436.

3 files changed, 54 insertions, 21 deletions

diff --git a/include/usage.h b/include/usage.h
index 3ef421197..6b54a1266 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -3686,22 +3686,24 @@ USE_FEATURE_RUN_PARTS_FANCY("\n	-l	Prints names of all matching files even when
        "[OPTION]..."
 #define syslogd_full_usage \
        "System logging utility.\n" \
-       "Note that this version of syslogd ignores /etc/syslog.conf." \
-       "\n\nOptions:" \
-       "\n      -n              Run in foreground" \
-       "\n      -O FILE         Log to given file (default=/var/log/messages)" \
-       "\n      -l n            Set local log level" \
-       "\n      -S              Smaller logging output" \
+       "Note that this version of syslogd ignores /etc/syslog.conf.\n" \
+     "\nOptions:" \
+     "\n        -n              Run in foreground" \
+     "\n        -O FILE         Log to given file (default=/var/log/messages)" \
+     "\n        -l n            Set local log level" \
+     "\n        -S              Smaller logging output" \
         USE_FEATURE_ROTATE_LOGFILE( \
-       "\n      -s SIZE         Max size (KB) before rotate (default=200KB, 0=off)" \
-       "\n      -b NUM          Number of rotated logs to keep (default=1, max=99, 0=purge)") \
+     "\n        -s SIZE         Max size (KB) before rotate (default=200KB, 0=off)" \
+     "\n        -b NUM          Number of rotated logs to keep (default=1, max=99, 0=purge)") \
         USE_FEATURE_REMOTE_LOG( \
-       "\n      -R HOST[:PORT]  Log to IP or hostname on PORT (default PORT=514/UDP)" \
-       "\n      -L              Log locally and via network (default is network only if -R)") \
+     "\n        -R HOST[:PORT]  Log to IP or hostname on PORT (default PORT=514/UDP)" \
+     "\n        -L              Log locally and via network (default is network only if -R)") \
+        USE_FEATURE_SYSLOGD_DUP( \
+     "\n        -D              Drop duplicates") \
         USE_FEATURE_IPC_SYSLOG( \
-       "\n      -C[size(KiB)]   Log to shared mem buffer (read it using logread)")
+     "\n        -C[size(KiB)]   Log to shared mem buffer (read it using logread)")
         /* NB: -Csize shouldn't have space (because size is optional) */
-/*     "\n      -m MIN          Minutes between MARK lines (default=20, 0=off)" */
+/*   "\n        -m MIN          Minutes between MARK lines (default=20, 0=off)" */
 #define syslogd_example_usage \
        "$ syslogd -R masterlog:514\n" \
        "$ syslogd -R 192.168.1.1:601\n"
diff --git a/sysklogd/Config.in b/sysklogd/Config.in
index 78097eea1..45f86ed62 100644
--- a/sysklogd/Config.in
+++ b/sysklogd/Config.in
@@ -42,6 +42,14 @@ config FEATURE_REMOTE_LOG
           measure to prevent system logs from being tampered with
           by an intruder.
 
+config FEATURE_SYSLOGD_DUP
+        bool "Support -D (drop dups) option"
+        default n
+        depends on SYSLOGD
+        help
+          Option -D instructs syslogd to drop consecutive messages
+          which are totally the same.
+
 config FEATURE_IPC_SYSLOG
         bool "Circular Buffer support"
         default n
diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index 0d004bc27..e54ade7fd 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -101,7 +101,7 @@ struct globals {
         char *hostname;
 
         /* We recv into recvbuf... */
-        char recvbuf[MAX_READ];
+        char recvbuf[MAX_READ * (1 + ENABLE_FEATURE_SYSLOGD_DUP)];
         /* ...then copy to parsebuf, escaping control chars */
         /* (can grow x2 max) */
         char parsebuf[MAX_READ*2];
@@ -152,6 +152,7 @@ enum {
         USE_FEATURE_REMOTE_LOG(    OPTBIT_remote     ,) // -R
         USE_FEATURE_REMOTE_LOG(    OPTBIT_locallog   ,) // -L
         USE_FEATURE_IPC_SYSLOG(    OPTBIT_circularlog,) // -C
+        USE_FEATURE_SYSLOGD_DUP(   OPTBIT_dup        ,) // -D
 
         OPT_mark        = 1 << OPTBIT_mark    ,
         OPT_nofork      = 1 << OPTBIT_nofork  ,
@@ -163,13 +164,15 @@ enum {
         OPT_remotelog   = USE_FEATURE_REMOTE_LOG(    (1 << OPTBIT_remote     )) + 0,
         OPT_locallog    = USE_FEATURE_REMOTE_LOG(    (1 << OPTBIT_locallog   )) + 0,
         OPT_circularlog = USE_FEATURE_IPC_SYSLOG(    (1 << OPTBIT_circularlog)) + 0,
+        OPT_dup         = USE_FEATURE_SYSLOGD_DUP(   (1 << OPTBIT_dup        )) + 0,
 };
 #define OPTION_STR "m:nO:l:S" \
         USE_FEATURE_ROTATE_LOGFILE("s:" ) \
         USE_FEATURE_ROTATE_LOGFILE("b:" ) \
         USE_FEATURE_REMOTE_LOG(    "R:" ) \
         USE_FEATURE_REMOTE_LOG(    "L"  ) \
-        USE_FEATURE_IPC_SYSLOG(    "C::")
+        USE_FEATURE_IPC_SYSLOG(    "C::") \
+        USE_FEATURE_SYSLOGD_DUP(   "D"  )
 #define OPTION_DECL *opt_m, *opt_l \
         USE_FEATURE_ROTATE_LOGFILE(,*opt_s) \
         USE_FEATURE_ROTATE_LOGFILE(,*opt_b) \
@@ -538,6 +541,13 @@ static void do_syslogd(void) ATTRIBUTE_NORETURN;
 static void do_syslogd(void)
 {
         int sock_fd;
+#if ENABLE_FEATURE_SYSLOGD_DUP
+        int last_sz = -1;
+        char *last_buf;
+        char *recvbuf = G.recvbuf;
+#else
+#define recvbuf (G.recvbuf)
+#endif
 
         /* Set up signal handlers */
         bb_signals(0
@@ -561,8 +571,16 @@ static void do_syslogd(void)
 
         for (;;) {
                 size_t sz;
+
+#if ENABLE_FEATURE_SYSLOGD_DUP
+                last_buf = recvbuf;
+                if (recvbuf == G.recvbuf)
+                        recvbuf = G.recvbuf + MAX_READ;
+                else
+                        recvbuf = G.recvbuf;
+#endif
  read_again:
-                sz = safe_read(sock_fd, G.recvbuf, MAX_READ - 1);
+                sz = safe_read(sock_fd, recvbuf, MAX_READ - 1);
                 if (sz < 0)
                         bb_perror_msg_and_die("read from /dev/log");
 
@@ -577,11 +595,16 @@ static void do_syslogd(void)
                          * IOW: newline is passed verbatim!
                          * I take it to mean that it's syslogd's job
                          * to make those look identical in the log files. */
-                        if (G.recvbuf[sz-1] != '\0' && G.recvbuf[sz-1] != '\n')
+                        if (recvbuf[sz-1] != '\0' && recvbuf[sz-1] != '\n')
                                 break;
                         sz--;
                 }
-                /* TODO: maybe suppress duplicates? */
+#if ENABLE_FEATURE_SYSLOGD_DUP
+                if ((option_mask32 & OPT_dup) && (sz == last_sz))
+                        if (memcmp(last_buf, recvbuf, sz) == 0)
+                                continue;
+                last_sz = sz;
+#endif
 #if ENABLE_FEATURE_REMOTE_LOG
                 /* We are not modifying log messages in any way before send */
                 /* Remote site cannot trust _us_ anyway and need to do validation again */
@@ -593,18 +616,18 @@ static void do_syslogd(void)
                         }
                         /* Stock syslogd sends it '\n'-terminated
                          * over network, mimic that */
-                        G.recvbuf[sz] = '\n';
+                        recvbuf[sz] = '\n';
                         /* send message to remote logger, ignore possible error */
                         /* TODO: on some errors, close and set G.remoteFD to -1
                          * so that DNS resolution and connect is retried? */
-                        sendto(G.remoteFD, G.recvbuf, sz+1, MSG_DONTWAIT,
+                        sendto(G.remoteFD, recvbuf, sz+1, MSG_DONTWAIT,
                                     &G.remoteAddr->u.sa, G.remoteAddr->len);
  no_luck: ;
                 }
 #endif
                 if (!ENABLE_FEATURE_REMOTE_LOG || (option_mask32 & OPT_locallog)) {
-                        G.recvbuf[sz] = '\0'; /* ensure it *is* NUL terminated */
-                        split_escape_and_log(G.recvbuf, sz);
+                        recvbuf[sz] = '\0'; /* ensure it *is* NUL terminated */
+                        split_escape_and_log(recvbuf, sz);
                 }
         } /* for (;;) */
 }