Commit 7656d684 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

tcp: Add saw_unknown to struct tcp_options_received 



In a later patch, the bpf prog only wants to be called to handle
a header option if that particular header option cannot be handled by
the kernel.  This unknown option could be written by the peer's bpf-prog.
It could also be a new standard option that the running kernel does not
support it while a bpf-prog can handle it.

This patch adds a "saw_unknown" bit to "struct tcp_options_received"
and it uses an existing one byte hole to do that.  "saw_unknown" will
be set in tcp_parse_options() if it sees an option that the kernel
cannot handle.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200820190033.2884430-1-kafai@fb.com
parent ca584ba0

include/linux/tcp.h

+2 −0
Original line number Diff line number Diff line
@@ -92,6 +92,8 @@ struct tcp_options_received { 
		smc_ok : 1,	/* SMC seen on SYN packet		*/

		snd_wscale : 4,	/* Window scaling received from sender	*/

		rcv_wscale : 4;	/* Window scaling to send to receiver	*/

	u8	saw_unknown:1,	/* Received unknown option		*/

		unused:7;

	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 */

net/ipv4/tcp_input.c

+16 −6
Original line number Diff line number Diff line
@@ -3801,7 +3801,7 @@ static void tcp_parse_fastopen_option(int len, const unsigned char *cookie, 
	foc->exp = exp_opt;

}



static void smc_parse_options(const struct tcphdr *th,

static bool smc_parse_options(const struct tcphdr *th,

			      struct tcp_options_received *opt_rx,

			      const unsigned char *ptr,

			      int opsize)
@@ -3810,10 +3810,13 @@ static void smc_parse_options(const struct tcphdr *th, 
	if (static_branch_unlikely(&tcp_have_smc)) {

		if (th->syn && !(opsize & 1) &&

		    opsize >= TCPOLEN_EXP_SMC_BASE &&

		    get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC)

		    get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC) {

			opt_rx->smc_ok = 1;

			return true;

		}

	}

#endif

	return false;

}



/* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped
@@ -3874,6 +3877,7 @@ void tcp_parse_options(const struct net *net, 


	ptr = (const unsigned char *)(th + 1);

	opt_rx->saw_tstamp = 0;

	opt_rx->saw_unknown = 0;



	while (length > 0) {

		int opcode = *ptr++;
@@ -3964,15 +3968,21 @@ void tcp_parse_options(const struct net *net, 
				 */

				if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE &&

				    get_unaligned_be16(ptr) ==

				    TCPOPT_FASTOPEN_MAGIC)

				    TCPOPT_FASTOPEN_MAGIC) {

					tcp_parse_fastopen_option(opsize -

						TCPOLEN_EXP_FASTOPEN_BASE,

						ptr + 2, th->syn, foc, true);

				else

					smc_parse_options(th, opt_rx, ptr,

							  opsize);

					break;

				}



				if (smc_parse_options(th, opt_rx, ptr, opsize))

					break;



				opt_rx->saw_unknown = 1;

				break;



			default:

				opt_rx->saw_unknown = 1;

			}

			ptr += opsize-2;

			length -= opsize;

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