tcp: options clean up
This should fix the following bugs:
* Connections with MD5 signatures produce invalid packets whenever SACK
options are included
* MD5 signatures are counted twice in the MSS calculations
Behaviour changes:
* A SYN with MD5 + SACK + TS elicits a SYNACK with MD5 + SACK
This is because we can't fit any SACK blocks in a packet with MD5 + TS
options. There was discussion about disabling SACK rather than TS in
order to fit in better with old, buggy kernels, but that was deemed to
be unnecessary.
* SYNs with MD5 don't include a TS option
See above.
Additionally, it removes a bunch of duplicated logic for calculating options,
which should help avoid these sort of issues in the future.
Signed-off-by: Adam Langley <agl@imperialviolet.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 31f5bbf..8983386 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -50,6 +50,7 @@
extern void tcp_time_wait(struct sock *sk, int state, int timeo);
#define MAX_TCP_HEADER (128 + MAX_HEADER)
+#define MAX_TCP_OPTION_SPACE 40
/*
* Never offer a window over 32767 without using window scaling. Some
@@ -184,6 +185,7 @@
#define TCPOLEN_SACK_BASE_ALIGNED 4
#define TCPOLEN_SACK_PERBLOCK 8
#define TCPOLEN_MD5SIG_ALIGNED 20
+#define TCPOLEN_MSS_ALIGNED 4
/* Flags in tp->nonagle */
#define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */
