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Subject[PATCH v4 7/7] TCPCT part 2g: parse cookie pair and 64-bit timestamp
Parse cookie pair extended option (previously defined).

Define and parse 64-bit timestamp extended option (and minor cleanup).
However, only 32-bits are used at this time (permitted by specification).

Every bit is sacred. Use as few bits as possible in the tcp_sock
structure, at the expense of performance.

Requires:
net: tcp_header_len_th and tcp_option_len_th
TCPCT part 2f: cleanup tcp_parse_options

Signed-off-by: William.Allen.Simpson@gmail.com
---
include/linux/tcp.h | 10 ++++-
include/net/tcp.h | 45 ++++++++++---------
net/ipv4/tcp_input.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++----
3 files changed, 142 insertions(+), 32 deletions(-)From bf57376550e7d5ae3d2342a619fdfc8ae2162e3b Mon Sep 17 00:00:00 2001
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 2987ee8..b71be6c 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -260,13 +260,21 @@ struct tcp_options_received {
u8 num_sacks; /* Number of SACK blocks */
u16 user_mss; /* mss requested by user in ioctl */
u16 mss_clamp; /* Maximal mss, negotiated at connection setup */
+
+ /* When the options are extended beyond the maximum 40 bytes,
+ * then this holds the additional data offset (in 32-bit words).
+ */
+ u16 extended:12, /* Up to 3,315 = 13 (40/3) by 255 */
+ saw_tstamp64:1, /* Seen on recent packet */
+ tstamp64_ok:1, /* Verified with cookie pair */
+ __unused:2;
};

static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
{
rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
- rx_opt->cookie_plus = 0;
+ rx_opt->tstamp64_ok = 0;
}

/* This is the max number of SACKS that we'll generate and process. It's safe
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 420e872..157c97b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -156,9 +156,8 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
/*
* TCP option
*/
-
-#define TCPOPT_NOP 1 /* Padding */
#define TCPOPT_EOL 0 /* End of options */
+#define TCPOPT_NOP 1 /* Padding */
#define TCPOPT_MSS 2 /* Segment size negotiating */
#define TCPOPT_WINDOW 3 /* Window scaling */
#define TCPOPT_SACK_PERM 4 /* SACK Permitted */
@@ -166,30 +165,32 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
#define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
#define TCPOPT_MD5SIG 19 /* MD5 Signature (RFC2385) */
#define TCPOPT_COOKIE 253 /* Cookie extension (experimental) */
-
-/*
- * TCP option lengths
- */
-
-#define TCPOLEN_MSS 4
-#define TCPOLEN_WINDOW 3
-#define TCPOLEN_SACK_PERM 2
-#define TCPOLEN_TIMESTAMP 10
-#define TCPOLEN_MD5SIG 18
-#define TCPOLEN_COOKIE_BASE 2 /* Cookie-less header extension */
-#define TCPOLEN_COOKIE_PAIR 3 /* Cookie pair header extension */
-#define TCPOLEN_COOKIE_MIN (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MIN)
-#define TCPOLEN_COOKIE_MAX (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MAX)
-
-/* But this is what stacks really send out. */
-#define TCPOLEN_TSTAMP_ALIGNED 12
+#define TCPOPT_TSTAMP64 254 /* 64-bit extension (experimental) */
+
+/* TCP option lengths (same order as above) */
+#define TCPOLEN_MSS 4
+#define TCPOLEN_WINDOW 3
+#define TCPOLEN_SACK_PERM 2
+#define TCPOLEN_SACK_BASE 2
+#define TCPOLEN_SACK_PERBLOCK 8
+#define TCPOLEN_TIMESTAMP 10
+#define TCPOLEN_MD5SIG 18
+#define TCPOLEN_COOKIE_BASE 2 /* Cookie-less header extension */
+#define TCPOLEN_COOKIE_PAIR 3 /* Cookie pair header extension */
+#define TCPOLEN_COOKIE_MIN (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MIN)
+#define TCPOLEN_COOKIE_MAX (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MAX)
+#define TCPOLEN_TSTAMP64 3
+
+/* TCP options 32-bit aligned (same order as above) */
+#define TCPOLEN_MSS_ALIGNED 4
#define TCPOLEN_WSCALE_ALIGNED 4
#define TCPOLEN_SACKPERM_ALIGNED 4
-#define TCPOLEN_SACK_BASE 2
#define TCPOLEN_SACK_BASE_ALIGNED 4
-#define TCPOLEN_SACK_PERBLOCK 8
+#define TCPOLEN_TSTAMP_ALIGNED 12
#define TCPOLEN_MD5SIG_ALIGNED 20
-#define TCPOLEN_MSS_ALIGNED 4
+
+/* TCP option extensions (same order as above) */
+#define TCPOEXT_TSTAMP64 16

/* Flags in tp->nonagle */
#define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d3c6c7a..86c49a4 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3722,9 +3722,71 @@ old_ack:
return 0;
}

+/* Process option extension data.
+ *
+ * Extension data in nonlinear skb is Not Yet Implemented!!!
+ *
+ * Returns:
+ * 0 on success
+ * - on failure
+ */
+int tcp_parse_extension(struct sk_buff *skb, const struct tcphdr *th,
+ struct tcp_options_received *opt_rx, u8 **hvpp)
+{
+ __be32 *tsp = (__be32 *)th + th->doff;
+ int remainder = skb_headlen(skb);
+
+ if (unlikely(th->syn)) {
+ /* Extended options are ignored on SYN or SYNACK, just as other
+ * malformed or unrecognized options. Leave the data in place.
+ */
+ opt_rx->extended = 0;
+ return 0;
+ }
+
+ /* Adjust end_seq, set in tcp_v[4,6]_rcv() */
+ TCP_SKB_CB(skb)->end_seq -= (opt_rx->extended * 4);
+
+ /* If present, always first, aligned */
+ if (opt_rx->saw_tstamp64) {
+ if (unlikely(remainder < TCPOEXT_TSTAMP64)) {
+ /* insufficient data */
+ opt_rx->saw_tstamp64 = 0 /* false */;
+ opt_rx->saw_tstamp = 0 /* false */;
+ } else {
+ /* 64-bits not yet implemented */
+ tsp++;
+ opt_rx->rcv_tsval = ntohl(*tsp);
+ tsp += 2;
+ opt_rx->rcv_tsecr = ntohl(*tsp);
+ tsp++;
+ }
+ remainder -= TCPOEXT_TSTAMP64;
+ }
+
+ /* If present, TCPOLEN_COOKIE_PAIR makes this an odd value */
+ if (opt_rx->cookie_plus & 0x1) {
+ int cookie_size = opt_rx->cookie_plus - TCPOLEN_COOKIE_PAIR;
+
+ if (unlikely(remainder < cookie_size)) {
+ /* insufficient data */
+ opt_rx->cookie_plus = 0;
+ } else {
+ *hvpp = (u8 *)tsp;
+ tsp += (cookie_size / 4);
+ }
+ remainder -= cookie_size;
+ }
+ return (remainder < 0) ? remainder : 0;
+}
+
/* Look for tcp options. Normally only called on SYN and SYNACK packets.
* But, this can also be called on packets in the established flow when
* the fast version below fails.
+ *
+ * Returns:
+ * 0 on success
+ * - on failure
*/
int tcp_parse_options(struct sk_buff *skb, const struct tcphdr *th,
struct tcp_options_received *opt_rx, u8 **hvpp, int estab)
@@ -3733,6 +3795,8 @@ int tcp_parse_options(struct sk_buff *skb, const struct tcphdr *th,
int length = tcp_option_len_th(th);

opt_rx->cookie_plus = 0;
+ opt_rx->extended = 0;
+ opt_rx->saw_tstamp64 = 0; /* false */
opt_rx->saw_tstamp = 0; /* false */

while (length > 0) {
@@ -3741,6 +3805,9 @@ int tcp_parse_options(struct sk_buff *skb, const struct tcphdr *th,

switch (opcode) {
case TCPOPT_EOL:
+ if (opt_rx->extended > 0)
+ return tcp_parse_extension(skb, th, opt_rx,
+ hvpp);
return 0;
case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
length--;
@@ -3753,6 +3820,9 @@ int tcp_parse_options(struct sk_buff *skb, const struct tcphdr *th,
opsize = *ptr++;
if (opsize < 2 || opsize > length) {
/* don't parse partial options */
+ if (opt_rx->extended > 0)
+ return tcp_parse_extension(skb, th, opt_rx,
+ hvpp);
return 0;
}

@@ -3829,7 +3899,16 @@ int tcp_parse_options(struct sk_buff *skb, const struct tcphdr *th,
/* not yet implemented */
break;
case TCPOLEN_COOKIE_PAIR:
- /* not yet implemented */
+ if (*ptr >= (TCPOLEN_COOKIE_MIN / 4) &&
+ *ptr <= (TCPOLEN_COOKIE_MAX / 4) &&
+ !th->syn && opt_rx->saw_tstamp &&
+ opt_rx->cookie_plus == 0 &&
+ (opt_rx->extended == 0 ||
+ (opt_rx->extended == (TCPOEXT_TSTAMP64 / 4) &&
+ opt_rx->saw_tstamp64))) {
+ opt_rx->cookie_plus = opsize + *ptr;
+ }
+ opt_rx->extended += *ptr;
break;
case TCPOLEN_COOKIE_MIN+0:
case TCPOLEN_COOKIE_MIN+2:
@@ -3849,6 +3928,18 @@ int tcp_parse_options(struct sk_buff *skb, const struct tcphdr *th,
};
break;

+ case TCPOPT_TSTAMP64:
+ if (opsize == TCPOLEN_TSTAMP64) {
+ if (*ptr == (TCPOEXT_TSTAMP64 / 4) &&
+ !th->syn && !opt_rx->saw_tstamp &&
+ opt_rx->extended == 0) {
+ opt_rx->saw_tstamp64 = 1; /* true */
+ opt_rx->saw_tstamp = 1; /* true */
+ }
+ opt_rx->extended += *ptr;
+ }
+ break;
+
default:
/* skip unrecognized options */
break;
@@ -3857,6 +3948,8 @@ int tcp_parse_options(struct sk_buff *skb, const struct tcphdr *th,
ptr += opsize - 2;
length -= opsize;
}
+ if (opt_rx->extended > 0)
+ return tcp_parse_extension(skb, th, opt_rx, hvpp);
return 0;
}

@@ -3883,6 +3976,11 @@ static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th)

/* Fast parse options. This hopes to only see timestamps.
* If it is wrong it falls back on tcp_parse_options().
+ *
+ * Returns:
+ * 1 on success, fast
+ * 0 on success, slow
+ * - on failure
*/
static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
struct tcp_sock *tp, u8 **hvpp)
@@ -3892,11 +3990,14 @@ static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
*/
if (th->doff == (sizeof(*th) / 4)) {
tp->rx_opt.saw_tstamp = 0;
+ tp->rx_opt.extended = 0;
return 0;
- } else if (tp->rx_opt.tstamp_ok &&
- th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
- if (tcp_parse_aligned_timestamp(tp, th))
- return 1;
+ }
+ if (th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4) &&
+ tp->rx_opt.tstamp_ok &&
+ tcp_parse_aligned_timestamp(tp, th)) {
+ tp->rx_opt.extended = 0;
+ return 1;
}
return tcp_parse_options(skb, th, &tp->rx_opt, hvpp, 1);
}
@@ -3907,8 +4008,8 @@ static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
*/
u8 *tcp_parse_md5sig_option(struct tcphdr *th)
{
- int length = (th->doff << 2) - sizeof (*th);
u8 *ptr = (u8*)(th + 1);
+ int length = tcp_option_len_th(th);

/* If the TCP option is too short, we can short cut */
if (length < TCPOLEN_MD5SIG)
@@ -4373,7 +4474,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
goto drop;

- __skb_pull(skb, th->doff * 4);
+ __skb_pull(skb, (th->doff + tp->rx_opt.extended) * 4);

TCP_ECN_accept_cwr(tp, skb);

@@ -5034,8 +5135,8 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)

/* Do we wait for any urgent data? - normally not... */
if (tp->urg_data == TCP_URG_NOTYET) {
- u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
- th->syn;
+ u32 ptr = ((th->doff + tp->rx_opt.extended) * 4)
+ + tp->urg_seq - ntohl(th->seq) - th->syn;

/* Is the urgent pointer pointing into this packet? */
if (ptr < skb->len) {
--
1.6.3.3
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