netflow: Document 1400-byte packet length limit.

The NetFlow code accumulates records until the packet is 1400 bytes or
some amount of time has passed.  This just adds a comment that NetFlow
messages are limited to 30 records, which places a ceiling on how large
the message can be (1400 is below that ceiling).

diff --git a/secchan/netflow.c b/secchan/netflow.c
index dc83a9b0454f7c3db7648be18d449dcc6494aae1..b68a51ca8435a25694b2fc3ab3cf3832d64fef3c 100644 (file)
--- a/secchan/netflow.c
+++ b/secchan/netflow.c
@@ -227,6 +227,8 @@ netflow_expire(struct netflow *nf, const struct ofexpired *expired)
     nf_rec->ip_proto = expired->flow.nw_proto;
     nf_rec->ip_tos = expired->ip_tos;
 
+    /* NetFlow messages are limited to 30 records.  A length of 1400
+     * bytes guarantees that the limit is not exceeded.  */
     if (nf->packet.size >= 1400) {
         netflow_run(nf);
     }