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Message-ID: <ZNncdWeTgSuAuodC@Laptop-X1>
Date: Mon, 14 Aug 2023 15:49:09 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Andrea Mayer <andrea.mayer@...roma2.it>
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
David Ahern <dsahern@...nel.org>, Shuah Khan <shuah@...nel.org>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-kselftest@...r.kernel.org,
Stefano Salsano <stefano.salsano@...roma2.it>,
Paolo Lungaroni <paolo.lungaroni@...roma2.it>,
Ahmed Abdelsalam <ahabdels.dev@...il.com>
Subject: Re: [net-next v2 1/2] seg6: add NEXT-C-SID support for SRv6 End.X
behavior
On Sat, Aug 12, 2023 at 08:09:25PM +0200, Andrea Mayer wrote:
> The NEXT-C-SID mechanism described in [1] offers the possibility of
> encoding several SRv6 segments within a single 128 bit SID address. Such
> a SID address is called a Compressed SID (C-SID) container. In this way,
> the length of the SID List can be drastically reduced.
>
> A SID instantiated with the NEXT-C-SID flavor considers an IPv6 address
> logically structured in three main blocks: i) Locator-Block; ii)
> Locator-Node Function; iii) Argument.
>
> C-SID container
> +------------------------------------------------------------------+
> | Locator-Block |Loc-Node| Argument |
> | |Function| |
> +------------------------------------------------------------------+
> <--------- B -----------> <- NF -> <------------- A --------------->
>
> (i) The Locator-Block can be any IPv6 prefix available to the provider;
>
> (ii) The Locator-Node Function represents the node and the function to
> be triggered when a packet is received on the node;
>
> (iii) The Argument carries the remaining C-SIDs in the current C-SID
> container.
>
> This patch leverages the NEXT-C-SID mechanism previously introduced in the
> Linux SRv6 subsystem [2] to support SID compression capabilities in the
> SRv6 End.X behavior [3].
> An SRv6 End.X behavior with NEXT-C-SID flavor works as an End.X behavior
> but it is capable of processing the compressed SID List encoded in C-SID
> containers.
>
> An SRv6 End.X behavior with NEXT-C-SID flavor can be configured to support
> user-provided Locator-Block and Locator-Node Function lengths. In this
> implementation, such lengths must be evenly divisible by 8 (i.e. must be
> byte-aligned), otherwise the kernel informs the user about invalid
> values with a meaningful error code and message through netlink_ext_ack.
>
> If Locator-Block and/or Locator-Node Function lengths are not provided
> by the user during configuration of an SRv6 End.X behavior instance with
> NEXT-C-SID flavor, the kernel will choose their default values i.e.,
> 32-bit Locator-Block and 16-bit Locator-Node Function.
>
> [1] - https://datatracker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression
> [2] - https://lore.kernel.org/all/20220912171619.16943-1-andrea.mayer@uniroma2.it/
> [3] - https://datatracker.ietf.org/doc/html/rfc8986#name-endx-l3-cross-connect
>
> Signed-off-by: Andrea Mayer <andrea.mayer@...roma2.it>
> ---
> net/ipv6/seg6_local.c | 108 ++++++++++++++++++++++++++++++++++--------
> 1 file changed, 88 insertions(+), 20 deletions(-)
>
> diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
> index dd433cc265c8..24e2b4b494cb 100644
> --- a/net/ipv6/seg6_local.c
> +++ b/net/ipv6/seg6_local.c
> @@ -109,15 +109,19 @@ struct bpf_lwt_prog {
> #define next_csid_chk_lcnode_fn_bits(flen) \
> next_csid_chk_lcblock_bits(flen)
>
> +/* flag indicating that flavors are set up for a given End* behavior */
> +#define SEG6_F_LOCAL_FLAVORS SEG6_F_ATTR(SEG6_LOCAL_FLAVORS)
> +
> #define SEG6_F_LOCAL_FLV_OP(flvname) BIT(SEG6_LOCAL_FLV_OP_##flvname)
> +#define SEG6_F_LOCAL_FLV_NEXT_CSID SEG6_F_LOCAL_FLV_OP(NEXT_CSID)
> #define SEG6_F_LOCAL_FLV_PSP SEG6_F_LOCAL_FLV_OP(PSP)
>
> /* Supported RFC8986 Flavor operations are reported in this bitmask */
> #define SEG6_LOCAL_FLV8986_SUPP_OPS SEG6_F_LOCAL_FLV_PSP
>
> -/* Supported Flavor operations are reported in this bitmask */
> -#define SEG6_LOCAL_FLV_SUPP_OPS (SEG6_F_LOCAL_FLV_OP(NEXT_CSID) | \
> +#define SEG6_LOCAL_END_FLV_SUPP_OPS (SEG6_F_LOCAL_FLV_NEXT_CSID | \
> SEG6_LOCAL_FLV8986_SUPP_OPS)
> +#define SEG6_LOCAL_END_X_FLV_SUPP_OPS SEG6_F_LOCAL_FLV_NEXT_CSID
>
> struct seg6_flavors_info {
> /* Flavor operations */
> @@ -411,9 +415,72 @@ static int end_next_csid_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
> return input_action_end_finish(skb, slwt);
> }
>
> +static int input_action_end_x_finish(struct sk_buff *skb,
> + struct seg6_local_lwt *slwt)
> +{
> + seg6_lookup_nexthop(skb, &slwt->nh6, 0);
> +
> + return dst_input(skb);
> +}
> +
> +static int input_action_end_x_core(struct sk_buff *skb,
> + struct seg6_local_lwt *slwt)
> +{
> + struct ipv6_sr_hdr *srh;
> +
> + srh = get_and_validate_srh(skb);
> + if (!srh)
> + goto drop;
> +
> + advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> +
> + return input_action_end_x_finish(skb, slwt);
> +
> +drop:
> + kfree_skb(skb);
> + return -EINVAL;
> +}
> +
> +static int end_x_next_csid_core(struct sk_buff *skb,
> + struct seg6_local_lwt *slwt)
> +{
> + const struct seg6_flavors_info *finfo = &slwt->flv_info;
> + struct in6_addr *daddr = &ipv6_hdr(skb)->daddr;
> +
> + if (seg6_next_csid_is_arg_zero(daddr, finfo))
> + return input_action_end_x_core(skb, slwt);
> +
> + /* update DA */
> + seg6_next_csid_advance_arg(daddr, finfo);
> +
> + return input_action_end_x_finish(skb, slwt);
> +}
> +
> static bool seg6_next_csid_enabled(__u32 fops)
> {
> - return fops & BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID);
> + return fops & SEG6_F_LOCAL_FLV_NEXT_CSID;
> +}
> +
> +/* Processing of SRv6 End, End.X, and End.T behaviors can be extended through
> + * the flavors framework. These behaviors must report the subset of (flavor)
> + * operations they currently implement. In this way, if a user specifies a
> + * flavor combination that is not supported by a given End* behavior, the
> + * kernel refuses to instantiate the tunnel reporting the error.
> + */
> +static int seg6_flv_supp_ops_by_action(int action, __u32 *fops)
> +{
> + switch (action) {
> + case SEG6_LOCAL_ACTION_END:
> + *fops = SEG6_LOCAL_END_FLV_SUPP_OPS;
> + break;
> + case SEG6_LOCAL_ACTION_END_X:
> + *fops = SEG6_LOCAL_END_X_FLV_SUPP_OPS;
> + break;
> + default:
> + return -EOPNOTSUPP;
> + }
> +
> + return 0;
> }
>
> /* We describe the packet state in relation to the absence/presence of the SRH
> @@ -746,21 +813,14 @@ static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
> /* regular endpoint, and forward to specified nexthop */
> static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
> {
> - struct ipv6_sr_hdr *srh;
> -
> - srh = get_and_validate_srh(skb);
> - if (!srh)
> - goto drop;
> -
> - advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> -
> - seg6_lookup_nexthop(skb, &slwt->nh6, 0);
> + const struct seg6_flavors_info *finfo = &slwt->flv_info;
> + __u32 fops = finfo->flv_ops;
>
> - return dst_input(skb);
> + /* check for the presence of NEXT-C-SID since it applies first */
> + if (seg6_next_csid_enabled(fops))
> + return end_x_next_csid_core(skb, slwt);
>
> -drop:
> - kfree_skb(skb);
> - return -EINVAL;
> + return input_action_end_x_core(skb, slwt);
> }
>
> static int input_action_end_t(struct sk_buff *skb, struct seg6_local_lwt *slwt)
> @@ -1404,13 +1464,14 @@ static struct seg6_action_desc seg6_action_table[] = {
> .action = SEG6_LOCAL_ACTION_END,
> .attrs = 0,
> .optattrs = SEG6_F_LOCAL_COUNTERS |
> - SEG6_F_ATTR(SEG6_LOCAL_FLAVORS),
> + SEG6_F_LOCAL_FLAVORS,
> .input = input_action_end,
> },
> {
> .action = SEG6_LOCAL_ACTION_END_X,
> .attrs = SEG6_F_ATTR(SEG6_LOCAL_NH6),
> - .optattrs = SEG6_F_LOCAL_COUNTERS,
> + .optattrs = SEG6_F_LOCAL_COUNTERS |
> + SEG6_F_LOCAL_FLAVORS,
> .input = input_action_end_x,
> },
> {
> @@ -2070,7 +2131,8 @@ static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt,
> {
> struct seg6_flavors_info *finfo = &slwt->flv_info;
> struct nlattr *tb[SEG6_LOCAL_FLV_MAX + 1];
> - unsigned long fops;
> + int action = slwt->action;
> + __u32 fops, supp_fops;
> int rc;
>
> rc = nla_parse_nested_deprecated(tb, SEG6_LOCAL_FLV_MAX,
> @@ -2086,7 +2148,8 @@ static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt,
> return -EINVAL;
>
> fops = nla_get_u32(tb[SEG6_LOCAL_FLV_OPERATION]);
> - if (fops & ~SEG6_LOCAL_FLV_SUPP_OPS) {
> + rc = seg6_flv_supp_ops_by_action(action, &supp_fops);
> + if (rc < 0 || (fops & ~supp_fops)) {
> NL_SET_ERR_MSG(extack, "Unsupported Flavor operation(s)");
> return -EOPNOTSUPP;
> }
> @@ -2618,6 +2681,11 @@ int __init seg6_local_init(void)
> */
> BUILD_BUG_ON(SEG6_LOCAL_MAX + 1 > BITS_PER_TYPE(unsigned long));
>
> + /* Check whether the number of defined flavors exceeds the maximum
> + * allowed value.
> + */
> + BUILD_BUG_ON(SEG6_LOCAL_FLV_OP_MAX + 1 > BITS_PER_TYPE(__u32));
> +
> /* If the default NEXT-C-SID Locator-Block/Node Function lengths (in
> * bits) have been changed with invalid values, kernel build stops
> * here.
> --
> 2.20.1
>
Reviewed-by: Hangbin Liu <liuhangbin@...il.com>
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