diff mbox series

[RFC,v4,bpf-next,04/12] tcp: Add saw_unknown to struct tcp_options_received

Message ID 20200803231039.2682896-1-kafai@fb.com
State RFC
Delegated to: BPF Maintainers
Headers show
Series BPF TCP header options | expand

Commit Message

Martin KaFai Lau Aug. 3, 2020, 11:10 p.m. UTC 
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: Martin KaFai Lau <kafai@fb.com>
---
 include/linux/tcp.h  |  2 ++
 net/ipv4/tcp_input.c | 22 ++++++++++++++++------
 2 files changed, 18 insertions(+), 6 deletions(-)

Comments

Eric Dumazet Aug. 4, 2020, 12:21 a.m. UTC | #1 
On Mon, Aug 3, 2020 at 4:10 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> 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: Martin KaFai Lau <kafai@fb.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@google.com>
John Fastabend Aug. 4, 2020, 1:14 a.m. UTC | #2 
Martin KaFai Lau wrote:
> 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: Martin KaFai Lau <kafai@fb.com>
> ---

Acked-by: John Fastabend <john.fastabend@gmail.com>
diff mbox series

Patch

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 5528912dc468..981145691f60 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -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 */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 05d0818c3e31..c1d2fb507701 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3799,7 +3799,7 @@  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)
@@ -3808,10 +3808,13 @@  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
@@ -3872,6 +3875,7 @@  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++;
@@ -3962,15 +3966,21 @@  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;