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Date: Fri, 28 Jun 2024 09:46:28 +0000
From: Asbjørn Sloth Tønnesen <ast@...erby.net>
To: Davide Caratti <dcaratti@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, aclaudi@...hat.com,
 Ilya Maximets <i.maximets@....org>, echaudro@...hat.com,
 netdev@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [RFC iproute2-next] tc: f_flower: add support for matching on
 tunnel metadata

Hi Davide,

Thank you for the patch.

Overall I think it looks good, I only have a few comments.

On 6/27/24 4:55 PM, Davide Caratti wrote:
> extend TC flower for matching on tunnel metadata.
> smoke test:
> 
>   # ip link add name myep type dummy
>   # ip link set dev myep up
>   # ip address add dev myep 192.0.2.1/24
>   # ip neigh add dev myep 192.0.2.2 lladdr 00:c1:a0:c1:a0:00 nud permanent
>   # ip link add name mytun type vxlan external
>   # ip link set dev mytun up
>   # tc qdisc add dev mytun clsact
>   # tc filter add dev mytun egress protocol ip pref 1 handle 1 matchall action tunnel_key \
>   >    set src_ip 192.0.2.1 dst_ip 192.0.2.2 id 42 csum nofrag continue index 1
>   # tc filter add dev mytun egress protocol ip pref 2 handle 2 flower action continue index 30
>   # tc filter add dev mytun egress protocol ip pref 3 handle 3 flower enc_src_ip 192.0.2.1 action continue index 30
>   # tc filter add dev mytun egress protocol ip pref 4 handle 4 flower enc_flags tundf action pipe index 100
>   # mausezahn mytun -c 1 -p 100 -a 00:aa:bb:cc:dd:ee -b 00:ee:dd:cc:bb:aa -t icmp -q
>   # expect 2 packets below
>   # tc -s action get action gact index 30
>   # expect 1 packet below
>   # tc -s action get action gact index 100
> 
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>
> ---
>   include/uapi/linux/pkt_cls.h |  8 +++++++
>   tc/f_flower.c                | 42 ++++++++++++++++++++++++++++++++++++
>   2 files changed, 50 insertions(+)
> 
> diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
> index 229fc925ec3a..24795aad7651 100644
> --- a/include/uapi/linux/pkt_cls.h
> +++ b/include/uapi/linux/pkt_cls.h
> @@ -554,6 +554,9 @@ enum {
>   	TCA_FLOWER_KEY_SPI,		/* be32 */
>   	TCA_FLOWER_KEY_SPI_MASK,	/* be32 */
>   
> +	TCA_FLOWER_KEY_ENC_FLAGS,	/* u32 */
> +	TCA_FLOWER_KEY_ENC_FLAGS_MASK,	/* u32 */
> +

FYI: I will do a v1 of the kernel side soon, where the comments
above will change to be32.

>   	__TCA_FLOWER_MAX,
>   };
>   
> @@ -674,6 +677,11 @@ enum {
>   enum {
>   	TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT = (1 << 0),
>   	TCA_FLOWER_KEY_FLAGS_FRAG_IS_FIRST = (1 << 1),
> +	/* FLOW_DIS_ENCAPSULATION (1 << 2) is not exposed to userspace */
> +	TCA_FLOWER_KEY_FLAGS_TUNNEL_CSUM = (1 << 3),
> +	TCA_FLOWER_KEY_FLAGS_TUNNEL_DONT_FRAGMENT = (1 << 4),
> +	TCA_FLOWER_KEY_FLAGS_TUNNEL_OAM = (1 << 5),
> +	TCA_FLOWER_KEY_FLAGS_TUNNEL_CRIT_OPT = (1 << 6),
>   };
>   
>   enum {
> diff --git a/tc/f_flower.c b/tc/f_flower.c
> index 08c1001af7b4..45fc31dc380f 100644
> --- a/tc/f_flower.c
> +++ b/tc/f_flower.c
> @@ -17,6 +17,7 @@
>   #include <linux/tc_act/tc_vlan.h>
>   #include <linux/mpls.h>
>   #include <linux/ppp_defs.h>
> +#include <linux/if_tunnel.h>
>   
>   #include "utils.h"
>   #include "tc_util.h"
> @@ -28,6 +29,7 @@
>   
>   enum flower_matching_flags {
>   	FLOWER_IP_FLAGS,
> +	FLOWER_ENC_DST_FLAGS,
>   };
>   
>   enum flower_endpoint {
> @@ -92,6 +94,7 @@ static void explain(void)
>   		"			erspan_opts MASKED-OPTIONS |\n"
>   		"			gtp_opts MASKED-OPTIONS |\n"
>   		"			pfcp_opts MASKED-OPTIONS |\n"
> +		"			enc_flags  ENC-FLAGS |\n"

Maybe add a "ENC-FLAGS := foo,bar,..." below, could be generated from flag_to_string[],
properly best to do separately as it requires moving the flag_to_string[] definition.

>   		"			ip_flags IP-FLAGS |\n"

IP-FLAGS is also not defined, properly a good time to fix that.

>   		"			l2_miss L2_MISS |\n"
>   		"			enc_dst_port [ port_number ] |\n"
> @@ -205,6 +208,11 @@ struct flag_to_string {
>   static struct flag_to_string flags_str[] = {
>   	{ TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT, FLOWER_IP_FLAGS, "frag" },
>   	{ TCA_FLOWER_KEY_FLAGS_FRAG_IS_FIRST, FLOWER_IP_FLAGS, "firstfrag" },
> +	{ TCA_FLOWER_KEY_FLAGS_TUNNEL_CSUM, FLOWER_ENC_DST_FLAGS, "csum" },
> +	{ TCA_FLOWER_KEY_FLAGS_TUNNEL_DONT_FRAGMENT, FLOWER_ENC_DST_FLAGS, "tundf" },
> +	{ TCA_FLOWER_KEY_FLAGS_TUNNEL_OAM, FLOWER_ENC_DST_FLAGS, "oam" },
> +	{ TCA_FLOWER_KEY_FLAGS_TUNNEL_CRIT_OPT, FLOWER_ENC_DST_FLAGS, "crit" },
> +

Nit: I would prefix all of these with "tun_".

>   };
>   
>   static int flower_parse_matching_flags(char *str,
> @@ -1461,6 +1469,29 @@ static int flower_parse_enc_opts_pfcp(char *str, struct nlmsghdr *n)
>   	return 0;
>   }
>   
> +static int flower_parse_enc_dstflags(char *str, struct nlmsghdr *n)
> +{
> +
> +	__u32 dst_flags, dst_flags_mask;
> +	int err;
> +
> +	err = flower_parse_matching_flags(str,
> +					  FLOWER_ENC_DST_FLAGS,
> +					  &dst_flags,
> +					  &dst_flags_mask);
> +
> +	if (err < 0 || !dst_flags_mask)
> +		return -1;
> +	err = addattr32(n, MAX_MSG, TCA_FLOWER_KEY_ENC_FLAGS, htonl(dst_flags));
> +	if (err < 0)
> +		return -1;
> +	err = addattr32(n, MAX_MSG, TCA_FLOWER_KEY_ENC_FLAGS_MASK, htonl(dst_flags_mask));
> +	if (err < 0)
> +		return -1;
> +
> +	return 0;
> +}
> +
>   static int flower_parse_mpls_lse(int *argc_p, char ***argv_p,
>   				 struct nlmsghdr *nlh)
>   {
> @@ -2248,6 +2279,13 @@ static int flower_parse_opt(const struct filter_util *qu, char *handle,
>   				fprintf(stderr, "Illegal \"pfcp_opts\"\n");
>   				return -1;
>   			}
> +		} else if (matches(*argv, "enc_flags") == 0) {
> +			NEXT_ARG();
> +			ret = flower_parse_enc_dstflags(*argv, n);
> +			if (ret < 0) {
> +				fprintf(stderr, "Illegal \"enc_flags\"\n");
> +				return -1;
> +			}

I agree that flower_parse_opt() is a bit crowded, but splitting it out to it's own function like this
implicitly also means that you can't specify enc_flags over multiple enc_flags argument, as addattr32()
is called once per enc_flags argument, instead of after all the arguments have been handled.

[..] flower ip_flags frag ip_flags firstfrag [..] is valid, and is equivalent to
[..] flower ip_flags frag/firstfrag [..].

IMHO I would completely mirror the way that ip_flags are handled, except the call to matches(),
so as to avoid adding any new quirks.


>   		} else if (matches(*argv, "action") == 0) {
>   			NEXT_ARG();
>   			ret = parse_action(&argc, &argv, TCA_FLOWER_ACT, n);
> @@ -3262,6 +3300,10 @@ static int flower_print_opt(const struct filter_util *qu, FILE *f,
>   				    tb[TCA_FLOWER_KEY_FLAGS],
>   				    tb[TCA_FLOWER_KEY_FLAGS_MASK]);
>   
> +	flower_print_matching_flags("enc_flags", FLOWER_ENC_DST_FLAGS,
> +				    tb[TCA_FLOWER_KEY_ENC_FLAGS],
> +				    tb[TCA_FLOWER_KEY_ENC_FLAGS_MASK]);
> +
>   	if (tb[TCA_FLOWER_L2_MISS]) {
>   		struct rtattr *attr = tb[TCA_FLOWER_L2_MISS];
>   

-- 
Best regards
Asbjørn Sloth Tønnesen
Network Engineer
Fiberby - AS42541

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