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@xxxxxxxxxxx/
[3] - https://datatracker.ietf.org/doc/html/rfc8986#name-endx-l3-cross-connect
Signed-off-by: Andrea Mayer <andrea.mayer@xxxxxxxxxxx>
---
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..ea7261872fae 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 = 0;
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 || !supp_fops || (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
