From: Nick Mathewson <nickm@torproject.org>
Date: Wed, 4 Aug 2010 18:54:38 +0000 (-0400)
Subject: Fix rate-limit calculation on openssl bufferevents.
X-Git-Tag: release-2.0.6-rc~11^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=009f300532481d4f3b7237f9a59fd306b371b8c0;p=libevent

Fix rate-limit calculation on openssl bufferevents.

When you're doing rate limiting on an openssl connection, you nearly
always want to limit the number of bytes sent and received over the
wire, not the number of bytes read or written over the secure
transport.
---

diff --git a/bufferevent_openssl.c b/bufferevent_openssl.c
index d89390d7..ae805004 100644
--- a/bufferevent_openssl.c
+++ b/bufferevent_openssl.c
@@ -273,6 +273,11 @@ BIO_new_bufferevent(struct bufferevent *bufferevent, int close_flag)
    we have a good way to get notified when they become readable/writable.)
    -------------------- */
 
+struct bio_data_counts {
+	unsigned long n_written;
+	unsigned long n_read;
+};
+
 struct bufferevent_openssl {
 	/* Shared fields with common bufferevent implementation code.
 	   If we were set up with an underlying bufferevent, we use the
@@ -290,6 +295,10 @@ struct bufferevent_openssl {
 	   know to write data to the SSL. */
 	struct evbuffer_cb_entry *outbuf_cb;
 
+	/* A count of how much data the bios have read/written total.  Used
+	   for rate-limiting. */
+	struct bio_data_counts counts;
+
 	/* If this value is greater than 0, then the last SSL_write blocked,
 	 * and we need to try it again with this many bytes. */
 	ev_ssize_t last_write;
@@ -525,6 +534,31 @@ conn_closed(struct bufferevent_openssl *bev_ssl, int errcode, int ret)
 	stop_writing(bev_ssl);
 }
 
+static void
+init_bio_counts(struct bufferevent_openssl *bev_ssl)
+{
+	bev_ssl->counts.n_written =
+	    BIO_number_written(SSL_get_wbio(bev_ssl->ssl));
+	bev_ssl->counts.n_read =
+	    BIO_number_read(SSL_get_wbio(bev_ssl->ssl));
+}
+
+static inline void
+decrement_buckets(struct bufferevent_openssl *bev_ssl)
+{
+	unsigned long num_w = BIO_number_written(SSL_get_wbio(bev_ssl->ssl));
+	unsigned long num_r = BIO_number_read(SSL_get_wbio(bev_ssl->ssl));
+	/* These next two subtractions can wrap around. That's okay. */
+	unsigned long w = num_w - bev_ssl->counts.n_written;
+	unsigned long r = num_r - bev_ssl->counts.n_read;
+	if (w)
+		_bufferevent_decrement_write_buckets(&bev_ssl->bev, w);
+	if (r)
+		_bufferevent_decrement_read_buckets(&bev_ssl->bev, r);
+	bev_ssl->counts.n_written = num_w;
+	bev_ssl->counts.n_read = num_r;
+}
+
 /* returns -1 on internal error, 0 on stall, 1 on progress */
 static int
 do_read(struct bufferevent_openssl *bev_ssl, int n_to_read)
@@ -553,9 +587,7 @@ do_read(struct bufferevent_openssl *bev_ssl, int n_to_read)
 					return -1;
 			++n_used;
 			space[i].iov_len = r;
-			/* Not exactly right; we probably want to do
-			 * our rate-limiting on the underlying bytes. */
-			_bufferevent_decrement_read_buckets(&bev_ssl->bev, r);
+			decrement_buckets(bev_ssl);
 		} else {
 			int err = SSL_get_error(bev_ssl->ssl, r);
 			print_err(err);
@@ -631,9 +663,7 @@ do_write(struct bufferevent_openssl *bev_ssl, int atmost)
 					return -1;
 			n_written += r;
 			bev_ssl->last_write = -1;
-			/* Not exactly right; we probably want to do
-			 * our rate-limiting on the underlying bytes. */
-			_bufferevent_decrement_write_buckets(&bev_ssl->bev, r);
+			decrement_buckets(bev_ssl);
 		} else {
 			int err = SSL_get_error(bev_ssl->ssl, r);
 			print_err(err);
@@ -855,6 +885,7 @@ do_handshake(struct bufferevent_openssl *bev_ssl)
 		r = SSL_do_handshake(bev_ssl->ssl);
 		break;
 	}
+	decrement_buckets(bev_ssl);
 
 	if (r==1) {
 		/* We're done! */
@@ -1167,6 +1198,8 @@ bufferevent_openssl_new_impl(struct event_base *base,
 	bev_ssl->state = state;
 	bev_ssl->last_write = -1;
 
+	init_bio_counts(bev_ssl);
+
 	switch (state) {
 	case BUFFEREVENT_SSL_ACCEPTING:
 		SSL_set_accept_state(bev_ssl->ssl);