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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2006-11-10 02:13:56 -0200
committerDavid S. Miller <davem@sunset.davemloft.net>2006-12-02 21:21:53 -0800
commit60361be1be7854cbffb6dc268d1bc094da33431c (patch)
tree58109e5c2020acfafd3c3e140620b7a93f0384ac /net/dccp/dccp.h
parent931731123a103cfb3f70ac4b7abfc71d94ba1f03 (diff)
[DCCP]: set safe upper bound for option length
This is a re-send from http://www.mail-archive.com/dccp@vger.kernel.org/msg00553.html It is the same patch as before, but I have built in Arnaldo's suggestions pointed out in that posting. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Diffstat (limited to 'net/dccp/dccp.h')
-rw-r--r--net/dccp/dccp.h18
1 files changed, 12 insertions, 6 deletions
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 272e8584564..9f00dd807e0 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -40,12 +40,18 @@ extern void dccp_tw_deschedule(struct inet_timewait_sock *tw);
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 MAX_DCCP_SPECIFIC_HEADER (255 * sizeof(int))
+#define DCCP_MAX_PACKET_HDR 28
+#define DCCP_MAX_OPT_LEN (MAX_DCCP_SPECIFIC_HEADER - DCCP_MAX_PACKET_HDR)
+#define MAX_DCCP_HEADER (MAX_DCCP_SPECIFIC_HEADER + MAX_HEADER)
#define DCCP_TIMEWAIT_LEN (60 * HZ) /* how long to wait to destroy TIME-WAIT
* state, about 60 seconds */