Commit b18afb6f authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Alexei Starovoitov
Browse files

tcp: Move tcp_ns_to_ts() to tcp.h 



We will support arbitrary SYN Cookie with BPF.

When BPF prog validates ACK and kfunc allocates a reqsk, we need
to call tcp_ns_to_ts() to calculate an offset of TSval for later
use:

  time
  t0 : Send SYN+ACK
       -> tsval = Initial TSval (Random Number)

  t1 : Recv ACK of 3WHS
       -> tsoff = TSecr - tcp_ns_to_ts(usec_ts_ok, tcp_clock_ns())
                = Initial TSval - t1

  t2 : Send ACK
       -> tsval = t2 + tsoff
                = Initial TSval + (t2 - t1)
                = Initial TSval + Time Delta (x)

  (x) Note that the time delta does not include the initial RTT
      from t0 to t1.

Let's move tcp_ns_to_ts() to tcp.h.

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240115205514.68364-2-kuniyu@amazon.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent d177c1be

include/net/tcp.h

+9 −0
Original line number Diff line number Diff line
@@ -577,6 +577,15 @@ static inline u32 tcp_cookie_time(void) 
	return val;

}



/* Convert one nsec 64bit timestamp to ts (ms or usec resolution) */

static inline u64 tcp_ns_to_ts(bool usec_ts, u64 val)

{

	if (usec_ts)

		return div_u64(val, NSEC_PER_USEC);



	return div_u64(val, NSEC_PER_MSEC);

}



u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,

			      u16 *mssp);

__u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);

net/ipv4/syncookies.c

+0 −9
Original line number Diff line number Diff line
@@ -51,15 +51,6 @@ static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport, 
			    count, &syncookie_secret[c]);

}



/* Convert one nsec 64bit timestamp to ts (ms or usec resolution) */

static u64 tcp_ns_to_ts(bool usec_ts, u64 val)

{

	if (usec_ts)

		return div_u64(val, NSEC_PER_USEC);



	return div_u64(val, NSEC_PER_MSEC);

}



/*

 * when syncookies are in effect and tcp timestamps are enabled we encode

 * tcp options in the lower bits of the timestamp value that will be