feat: source port validation

docs/troubleshooting/troubleshoot_SC4S_server.md

@@ -102,6 +102,19 @@ just _one_ bad index will "taint" the entire batch (in this case, 1000 events) a
 imperative that the container logs be free of these kinds of errors in production._ You can use the alternate HEC debug destination (below)
 to help debug this condition by sending direct "curl" commands to the HEC endpoint outside of the SC4S setting.
 
+## Invalid SC4S listen ports
+
+[SC4S exclusively grant a port to a device when `SC4S_LISTEN_{vendor}_{product}_{TCP/UDP/TLS}_PORT={port}`](https://splunk.github.io/splunk-connect-for-syslog/main/sources/#unique-listening-ports).
+
+During startup, SC4S validates that listening ports are configured correctly, and in case of misconfiguration, you will be able see any issues in container logs.
+
+You will receive an error message similar to the following if listening ports for `MERAKI SWITCHES` are configured incorrectly:
+```
+SC4S_LISTEN_MERAKI_SWITCHES_TCP_PORT: Wrong port number, don't use default port like (514,614,6514)
+SC4S_LISTEN_MERAKI_SWITCHES_UDP_PORT: 7000 is not unique and has already been used for another source
+SC4S_LISTEN_MERAKI_SWITCHES_TLS_PORT: 999999999999 must be integer within the range (0, 10000)
+```
+
 ##  SC4S Local Disk Resource Considerations
 * Check the HEC connection to Splunk. If the connection is down for a long period of time, the local disk buffer used for backup will exhaust local
 disk resources.  The size of the local disk buffer is configured in the env_file: [Disk buffer configuration](https://splunk-connect-for-syslog.readthedocs.io/en/latest/configuration/#disk-buffer-variables)

package/Dockerfile

@@ -76,6 +76,7 @@ COPY package/etc/local_config /etc/syslog-ng/local_config
 COPY package/etc/local_config /etc/syslog-ng/local_config
 COPY package/sbin/entrypoint.sh /
 COPY package/sbin/healthcheck.sh /
+COPY package/sbin/source_ports_validator.py /
 
 ENV SC4S_CONTAINER_OPTS=--no-caps
 ARG VERSION=unknown

package/Dockerfile.lite

@@ -98,6 +98,7 @@ COPY package/lite/etc/addons /etc/syslog-ng/addons
 
 COPY package/sbin/entrypoint.sh /
 COPY package/sbin/healthcheck.sh /
+COPY package/sbin/source_ports_validator.py /
 
 
 RUN chmod -R 755 /etc/syslog-ng/

package/sbin/entrypoint.sh

@@ -208,6 +208,8 @@ fi
 export SOURCE_SIMPLE_SET=$(printenv | grep '^SC4S_LISTEN_SIMPLE_.*_PORT=.' | sed 's/^SC4S_LISTEN_SIMPLE_//;s/_..._PORT\=.*//;s/_[^_]*_PORT\=.*//' | sort | uniq |  xargs echo | sed 's/ /,/g' | tr '[:upper:]' '[:lower:]' )
 export SOURCE_ALL_SET=$(printenv | grep '^SC4S_LISTEN_.*_PORT=.' | grep -v "disabled" | sed 's/^SC4S_LISTEN_//;s/_..._PORT\=.*//;s/_[^_]*_PORT\=.*//' | sort | uniq |  xargs echo | sed 's/ /,/g' | tr '[:lower:]' '[:upper:]' )
 
+python3 /source_ports_validator.py
+
 syslog-ng --no-caps --preprocess-into=- | grep vendor_product | grep set | grep -v 'set(.\$' | sed 's/^ *//' | grep 'value("fields.sc4s_vendor_product"' | grep -v "\`vendor_product\`" | sed s/^set\(// | cut -d',' -f1 | sed 's/\"//g' >/tmp/keys
 syslog-ng --no-caps --preprocess-into=- | grep 'meta_key(.' | sed 's/^ *meta_key(.//' | sed "s/')//" >>/tmp/keys
 rm -f $SC4S_ETC/conf.d/local/context/splunk_metadata.csv.example >/dev/null || true

package/sbin/source_ports_validator.py

@@ -0,0 +1,41 @@
+import collections
+import os
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+def is_valid_port(raw_port: str) -> bool:
+    return raw_port.isdigit() and 0 < int(raw_port) < 65565
+
+
+def validate_source_ports(sources: list[str]) -> None:
+    source_ports = {}
+    for source in sources:
+        for proto in ["TCP", "UDP", "TLS", "RFC5426", "RFC6587", "RFC5425"]:
+            source_ports[(source, proto)] = os.getenv(f"SC4S_LISTEN_{source}_{proto}_PORT", "disabled").split(",")
+
+
+    busy_ports_for_proto = collections.defaultdict(set)
+    for source, proto in source_ports.keys():        
+        for port in source_ports[(source, proto)]:
+            if not port or port == "disabled":
+                continue
+
+            elif not is_valid_port(port):
+                logger.error(f"SC4S_LISTEN_{source}_{proto}_PORT: {port} must be integer within the range (0, 65565)")
+
+            elif source != "DEFAULT" and port in source_ports[("DEFAULT", proto)]:
+                logger.error(f"SC4S_LISTEN_{source}_{proto}_PORT: Wrong {port} number, don't use default port like {port}")
+
+            elif port in busy_ports_for_proto[proto]:
+                logger.error(f"SC4S_LISTEN_{source}_{proto}_PORT: {port} is not unique and has already been used for another source")
+
+            else:
+                busy_ports_for_proto[proto].add(port)
+
+
+if __name__ == "__main__":
+    sources = os.getenv("SOURCE_ALL_SET").split(",")
+    validate_source_ports(sources)