stun

commit 113583661d4602da401c981ef2cdd2d4173140d5
parent a530a7d26665b113eb2d8fbdc887321dab1a2f75
Author: sin <sin@2f30.org>
Date:   Tue, 12 Apr 2016 15:17:58 +0100

some comments for netpkt.c

Diffstat:
M
netpkt.c
 | 
32
++++++++++++++++++++++++++++----

1 file changed, 28 insertions(+), 4 deletions(-)
diff --git a/netpkt.c b/netpkt.c
@@ -9,24 +9,39 @@
 
 #include "stun.h"
 
+/* the various state the input handler can be in */
 enum {
 	STATEINITIAL,
 	STATENONCE,
 	STATEHDR,
 	STATEPAYLOAD,
 	STATETAG,
-	STATEOPEN,
+	STATEDECRYPT,
 	STATEDISCARD
 };
 
+/* output buffer for writing data to the network */
 static unsigned char *wbuf;
+/* input buffer for reading data from the network */
 static unsigned char *rbuf;
-static size_t rbuftotal, rbufrem;
+
+/* total number of bytes read into input buffer */
+static size_t rbuftotal
+/* number of bytes remaining to read into buffer for current state */
+static size_t rbufrem;
+
+/* maximum input/output buffer size */
 static size_t maxbuflen;
+
+/* nonce size in bytes */
 static size_t noncelen;
+/* tag size in bytes */
 static size_t taglen;
+
+/* state tracking for input handling */
 static int state;
 
+/* create a packet and write it out to the network in one go */
 int
 netwrite(int fd, unsigned char *pt, size_t ptlen, size_t *outlen)
 {
@@ -44,6 +59,7 @@ netwrite(int fd, unsigned char *pt, size_t ptlen, size_t *outlen)
 	}
 	*outlen = ptlen;
 
+	/* spin until all data is written */
 	while (buflen > 0) {
 		n = write(fd, p + total, buflen);
 		if (n == 0) {
@@ -60,6 +76,10 @@ netwrite(int fd, unsigned char *pt, size_t ptlen, size_t *outlen)
 	return PKTCOMPLETE;
 }
 
+/*
+ * Since stun is using non-blocking sockets it needs to handle
+ * partial reads.  A state machine is devised for this purpose.
+ */
 int
 netread(int fd, unsigned char *pt, size_t ptlen, size_t *outlen)
 {
@@ -121,9 +141,9 @@ netread(int fd, unsigned char *pt, size_t ptlen, size_t *outlen)
 				rbufrem -= n;
 			}
 			if (rbufrem == 0)
-				state = STATEOPEN;
+				state = STATEDECRYPT;
 			break;
-		case STATEOPEN:
+		case STATEDECRYPT:
 			state = STATEINITIAL;
 			if (!cryptoopen(pt, outlen, ptlen, rbuf, noncelen,
 			                &rbuf[noncelen + HDRLEN],
@@ -151,6 +171,10 @@ out:
 	return PKTFAILED;
 }
 
+/*
+ * reset state machine, required when a fatal error occurs or when
+ * a client disconnects
+ */
 void
 netreset(void)
 {