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@uniroma2.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,
.optattrs = SEG6_F_LOCAL_COUNTERS,
.optattrs = SEG6_F_LOCAL_COUNTERS |SEG6_F_LOCAL_FLAVORS,@@ -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@gmail.com