refactor: break down long functions into focused helpers

Refactored five functions >50 lines by extracting focused helper functions,
improving code readability and maintainability:

1. netlog-journal.c: journal_read_input() (97 → ~60 lines)
   - Extracted parse_journal_fields(), parse_syslog_severity(),
     parse_syslog_facility()

2. netlog-protocol.c: format_rfc5424() (103 → ~50 lines)
   - Extracted set_priority_version_field(), set_timestamp_field(),
     set_string_field_with_separator(), set_structured_data_field(),
     set_message_length_field()

3. netlog-protocol.c: format_rfc3339() (67 → ~52 lines)
   - Extracted set_priority_field()
   - Reused set_timestamp_field()

4. systemd-netlogd.c: main() (86 → ~53 lines)
   - Extracted initialize_logging(), resolve_user_credentials(),
     initialize_ssl_manager(), run_event_loop()

5. netlog-ssl.c: ssl_verify_certificate_validity() (66 → ~36 lines)
   - Extracted extract_certificate_names(), check_certificate_chain_depth(),
     determine_verification_log_level()

All tests passing. No functional changes.

Author: ssahani

src/netlog/netlog-journal.c

@@ -88,28 +88,103 @@ static int parse_fieldv(
         return 0;
 }
 
+static int parse_journal_fields(Manager *m,
+                                char **message,
+                                char **identifier,
+                                char **hostname,
+                                char **pid,
+                                char **facility,
+                                char **priority,
+                                char **structured_data,
+                                char **msgid) {
+        const void *data;
+        size_t length;
+        int r;
+        size_t hostname_len = 0, identifier_len = 0, message_len = 0, priority_len = 0, facility_len = 0,
+                structured_data_len = 0, msgid_len = 0, pid_len = 0;
+        const ParseFieldVec fields[] = {
+                PARSE_FIELD_VEC_ENTRY("_PID=",                        pid,               &pid_len              ),
+                PARSE_FIELD_VEC_ENTRY("MESSAGE=",                     message,           &message_len          ),
+                PARSE_FIELD_VEC_ENTRY("PRIORITY=",                    priority,          &priority_len         ),
+                PARSE_FIELD_VEC_ENTRY("_HOSTNAME=",                   hostname,          &hostname_len         ),
+                PARSE_FIELD_VEC_ENTRY("SYSLOG_FACILITY=",             facility,          &facility_len         ),
+                PARSE_FIELD_VEC_ENTRY("SYSLOG_IDENTIFIER=",           identifier,        &identifier_len       ),
+                PARSE_FIELD_VEC_ENTRY("SYSLOG_STRUCTURED_DATA=",      structured_data,   &structured_data_len  ),
+                PARSE_FIELD_VEC_ENTRY("SYSLOG_MSGID",                 msgid,             &msgid_len            ),
+        };
+
+        JOURNAL_FOREACH_DATA_RETVAL(m->journal, data, length, r) {
+                r = parse_fieldv(data, length, fields, ELEMENTSOF(fields));
+                if (r < 0)
+                        return r;
+        }
+
+        if (IN_SET(r, -EBADMSG, -EADDRNOTAVAIL)) {
+                log_debug_errno(r, "Skipping message we can't read: %m");
+                return 0;
+        }
+
+        return r;
+}
+
+static int parse_syslog_severity(Manager *m, const char *priority, unsigned *sev) {
+        int r;
+
+        assert(sev);
+
+        if (!priority)
+                return 0;
+
+        r = safe_atou(priority, sev);
+        if (r < 0) {
+                log_debug("Failed to parse syslog priority: %s", priority);
+                return r;
+        }
+
+        if (*sev < _SYSLOG_LEVEL_MAX && ((UINT8_C(1) << *sev) & m->excluded_syslog_levels)) {
+                log_debug("Skipping message with excluded syslog level %s.", syslog_level_to_string(*sev));
+                return 1; /* filtered */
+        }
+
+        if (*sev > LOG_DEBUG)
+                *sev = JOURNAL_DEFAULT_SEVERITY;
+
+        return 0;
+}
+
+static int parse_syslog_facility(Manager *m, const char *facility, unsigned *fac) {
+        int r;
+
+        assert(fac);
+
+        if (!facility)
+                return 0;
+
+        r = safe_atou(facility, fac);
+        if (r < 0) {
+                log_debug("Failed to parse syslog facility: %s", facility);
+                return r;
+        }
+
+        if (*fac < _SYSLOG_FACILITY_MAX && ((UINT32_C(1) << *fac) & m->excluded_syslog_facilities)) {
+                log_debug("Skipping message with excluded syslog facility %s.", syslog_facility_to_string(*fac));
+                return 1; /* filtered */
+        }
+
+        if (*fac >= LOG_NFACILITIES)
+                *fac = JOURNAL_DEFAULT_FACILITY;
+
+        return 0;
+}
+
 static int journal_read_input(Manager *m) {
         _cleanup_free_ char *facility = NULL, *identifier = NULL, *priority = NULL, *message = NULL, *pid = NULL,
                 *hostname = NULL, *structured_data = NULL, *msgid = NULL, *cursor = NULL;
-        size_t hostname_len = 0, identifier_len = 0, message_len = 0, priority_len = 0, facility_len = 0,
-                structured_data_len = 0, msgid_len = 0, pid_len = 0;
         unsigned sev = JOURNAL_DEFAULT_SEVERITY;
         unsigned fac = JOURNAL_DEFAULT_FACILITY;
         struct timeval tv, *tvp = NULL;
-        const void *data;
         usec_t realtime;
-        size_t length;
         int r;
-        const ParseFieldVec fields[] = {
-                PARSE_FIELD_VEC_ENTRY("_PID=",                        &pid,               &pid_len              ),
-                PARSE_FIELD_VEC_ENTRY("MESSAGE=",                     &message,           &message_len          ),
-                PARSE_FIELD_VEC_ENTRY("PRIORITY=",                    &priority,          &priority_len         ),
-                PARSE_FIELD_VEC_ENTRY("_HOSTNAME=",                   &hostname,          &hostname_len         ),
-                PARSE_FIELD_VEC_ENTRY("SYSLOG_FACILITY=",             &facility,          &facility_len         ),
-                PARSE_FIELD_VEC_ENTRY("SYSLOG_IDENTIFIER=",           &identifier,        &identifier_len       ),
-                PARSE_FIELD_VEC_ENTRY("SYSLOG_STRUCTURED_DATA=",      &structured_data,   &structured_data_len  ),
-                PARSE_FIELD_VEC_ENTRY("SYSLOG_MSGID",                 &msgid,             &msgid_len            ),
-        };
 
         assert(m);
         assert(m->journal);
@@ -120,24 +195,18 @@ static int journal_read_input(Manager *m) {
 
         log_debug("Reading from journal cursor=%s", cursor);
 
-        JOURNAL_FOREACH_DATA_RETVAL(m->journal, data, length, r) {
-                r = parse_fieldv(data, length, fields, ELEMENTSOF(fields));
-                if (r < 0)
-                        return r;
-        }
-
-        if (IN_SET(r, -EBADMSG, -EADDRNOTAVAIL)) {
-                log_debug_errno(r, "Skipping message we can't read: %m");
-                return 0;
-        }
+        r = parse_journal_fields(m, &message, &identifier, &hostname, &pid, &facility, &priority, &structured_data, &msgid);
         if (r < 0)
                 return log_error_errno(r, "Failed to get journal fields: %m");
+        if (r == 0)
+                return 0;
 
         if (!message) {
                 log_debug("Skipping message without MESSAGE= field.");
                 return 0;
-        } else
-                log_debug("Received from journal MESSAGE='%s'", message);
+        }
+
+        log_debug("Received from journal MESSAGE='%s'", message);
 
         r = sd_journal_get_realtime_usec(m->journal, &realtime);
         if (r < 0)
@@ -150,31 +219,13 @@ static int journal_read_input(Manager *m) {
                 tvp = &tv;
         }
 
-        if (facility) {
-                r = safe_atou(facility, &fac);
-                if (r < 0)
-                        log_debug("Failed to parse syslog facility: %s", facility);
-                else if (fac < _SYSLOG_FACILITY_MAX && ((UINT32_C(1) << fac) & m->excluded_syslog_facilities)) {
-                        log_debug("Skipping message with excluded syslog facility %s.", syslog_facility_to_string(fac));
-                        return 0;
-                }
-
-                if (fac >= LOG_NFACILITIES)
-                        fac = JOURNAL_DEFAULT_FACILITY;
-        }
-
-        if (priority) {
-                r = safe_atou(priority, &sev);
-                if (r < 0)
-                        log_debug("Failed to parse syslog priority: %s", priority);
-                else if (sev < _SYSLOG_LEVEL_MAX && ((UINT8_C(1) << sev) & m->excluded_syslog_levels)) {
-                        log_debug("Skipping message with excluded syslog level %s.", syslog_level_to_string(sev));
-                        return 0;
-                }
+        r = parse_syslog_facility(m, facility, &fac);
+        if (r > 0) /* filtered */
+                return 0;
 
-                if (sev > LOG_DEBUG)
-                        sev = JOURNAL_DEFAULT_SEVERITY;
-        }
+        r = parse_syslog_severity(m, priority, &sev);
+        if (r > 0) /* filtered */
+                return 0;
 
         return manager_push_to_network(m,
                                        sev,