From: Gerrit Renker <gerrit@erg.abdn.ac.uk>
To: "Arnaldo Carvalho de Melo" <arnaldo.melo@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH 2.6.19] net/dccp: set safe upper bound for option length
Date: Fri, 22 Sep 2006 15:48:38 +0100 [thread overview]
Message-ID: <200609221548.38586@strip-the-willow> (raw)
In-Reply-To: <200609221545.03112@strip-the-willow>
Stupid me, it should read 4 * 255 = 1020, not 8 * 255; this is
fixed below.
--
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 272e858..adabf3e 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -40,12 +40,17 @@ extern void dccp_tw_deschedule(struct in
extern void dccp_time_wait(struct sock *sk, int state, int timeo);
-/* FIXME: Right size this */
-#define DCCP_MAX_OPT_LEN 128
-
-#define DCCP_MAX_PACKET_HDR 32
-
-#define MAX_DCCP_HEADER (DCCP_MAX_PACKET_HDR + DCCP_MAX_OPT_LEN + MAX_HEADER)
+/*
+ * Set safe upper bounds for header and option length. Since Data Offset is 8
+ * bits (RFC 4340, sec. 5.1), the total header length can never be more than
+ * 4 * 255 = 1020 bytes. The largest possible header length is 28 bytes (X=1):
+ * - DCCP-Response with ACK Subheader and 4 bytes of Service code OR
+ * - DCCP-Reset with ACK Subheader and 4 bytes of Reset Code fields
+ * Hence a safe upper bound for the maximum option length is 1020-28 = 992
+ */
+#define DCCP_MAX_OPT_LEN 992
+#define DCCP_MAX_PACKET_HDR 28
+#define MAX_DCCP_HEADER (1020 + MAX_HEADER)
#define DCCP_TIMEWAIT_LEN (60 * HZ) /* how long to wait to destroy TIME-WAIT
* state, about 60 seconds */
next prev parent reply other threads:[~2006-09-22 14:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-22 14:45 [PATCH 2.6.19] net/dccp: set safe upper bound for option length Gerrit Renker
2006-09-22 14:48 ` Gerrit Renker [this message]
-- strict thread matches above, loose matches on Subject: below --
2006-09-22 14:50 Arnaldo Carvalho de Melo
2006-09-22 14:50 ` Arnaldo Carvalho de Melo
2006-09-22 15:20 ` Gerrit Renker
2006-09-22 15:49 ` Arnaldo Carvalho de Melo
2006-09-22 19:41 ` Arnaldo Carvalho de Melo
2006-09-25 8:33 ` Gerrit Renker
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