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seg6: add NEXT-C-SID support for SRv6 End behavior 

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.

The NEXT-C-SID mechanism relies on the "flavors" framework defined in
[2]. The flavors represent additional operations that can modify or
extend a subset of the existing behaviors.

This patch introduces the support for flavors in SRv6 End behavior
implementing the NEXT-C-SID one. An SRv6 End behavior with NEXT-C-SID
flavor works as an End behavior but it is capable of processing the
compressed SID List encoded in C-SID containers.

An SRv6 End 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 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://datatracker.ietf.org/doc/html/rfc8986

Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Andrea Mayer 2022-09-12 19:16:18 +02:00 committed by Paolo Abeni
parent e2a8ecc451
commit 848f3c0d47
2 changed files with 356 additions and 3 deletions
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24
include/uapi/linux/seg6_local.h
View File

@ -28,6 +28,7 @@ enum {
SEG6_LOCAL_BPF,
SEG6_LOCAL_VRFTABLE,
SEG6_LOCAL_COUNTERS,
SEG6_LOCAL_FLAVORS,
__SEG6_LOCAL_MAX,
};
#define SEG6_LOCAL_MAX (__SEG6_LOCAL_MAX - 1)
@ -110,4 +111,27 @@ enum {
#define SEG6_LOCAL_CNT_MAX (__SEG6_LOCAL_CNT_MAX - 1)
/* SRv6 End* Flavor attributes */
enum {
SEG6_LOCAL_FLV_UNSPEC,
SEG6_LOCAL_FLV_OPERATION,
SEG6_LOCAL_FLV_LCBLOCK_BITS,
SEG6_LOCAL_FLV_LCNODE_FN_BITS,
__SEG6_LOCAL_FLV_MAX,
};
#define SEG6_LOCAL_FLV_MAX (__SEG6_LOCAL_FLV_MAX - 1)
/* Designed flavor operations for SRv6 End* Behavior */
enum {
SEG6_LOCAL_FLV_OP_UNSPEC,
SEG6_LOCAL_FLV_OP_PSP,
SEG6_LOCAL_FLV_OP_USP,
SEG6_LOCAL_FLV_OP_USD,
SEG6_LOCAL_FLV_OP_NEXT_CSID,
__SEG6_LOCAL_FLV_OP_MAX
};
#define SEG6_LOCAL_FLV_OP_MAX (__SEG6_LOCAL_FLV_OP_MAX - 1)
#endif

335
net/ipv6/seg6_local.c
View File

@ -73,6 +73,55 @@ struct bpf_lwt_prog {
char *name;
};
/* default length values (expressed in bits) for both Locator-Block and
* Locator-Node Function.
*
* Both SEG6_LOCAL_LCBLOCK_DBITS and SEG6_LOCAL_LCNODE_FN_DBITS *must* be:
* i) greater than 0;
* ii) evenly divisible by 8. In other terms, the lengths of the
* Locator-Block and Locator-Node Function must be byte-aligned (we can
* relax this constraint in the future if really needed).
*
* Moreover, a third condition must hold:
* iii) SEG6_LOCAL_LCBLOCK_DBITS + SEG6_LOCAL_LCNODE_FN_DBITS <= 128.
*
* The correctness of SEG6_LOCAL_LCBLOCK_DBITS and SEG6_LOCAL_LCNODE_FN_DBITS
* values are checked during the kernel compilation. If the compilation stops,
* check the value of these parameters to see if they meet conditions (i), (ii)
* and (iii).
*/
#define SEG6_LOCAL_LCBLOCK_DBITS 32
#define SEG6_LOCAL_LCNODE_FN_DBITS 16
/* The following next_csid_chk_{cntr,lcblock,lcblock_fn}_bits macros can be
* used directly to check whether the lengths (in bits) of Locator-Block and
* Locator-Node Function are valid according to (i), (ii), (iii).
*/
#define next_csid_chk_cntr_bits(blen, flen) \
((blen) + (flen) > 128)
#define next_csid_chk_lcblock_bits(blen) \
({ \
typeof(blen) __tmp = blen; \
(!__tmp || __tmp > 120 || (__tmp & 0x07)); \
})
#define next_csid_chk_lcnode_fn_bits(flen) \
next_csid_chk_lcblock_bits(flen)
/* Supported Flavor operations are reported in this bitmask */
#define SEG6_LOCAL_FLV_SUPP_OPS (BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID))
struct seg6_flavors_info {
/* Flavor operations */
__u32 flv_ops;
/* Locator-Block length, expressed in bits */
__u8 lcblock_bits;
/* Locator-Node Function length, expressed in bits*/
__u8 lcnode_func_bits;
};
enum seg6_end_dt_mode {
DT_INVALID_MODE = -EINVAL,
DT_LEGACY_MODE = 0,
@ -136,6 +185,8 @@ struct seg6_local_lwt {
#ifdef CONFIG_NET_L3_MASTER_DEV
struct seg6_end_dt_info dt_info;
#endif
struct seg6_flavors_info flv_info;
struct pcpu_seg6_local_counters __percpu *pcpu_counters;
int headroom;
@ -271,8 +322,50 @@ int seg6_lookup_nexthop(struct sk_buff *skb,
return seg6_lookup_any_nexthop(skb, nhaddr, tbl_id, false);
}
/* regular endpoint function */
static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
static __u8 seg6_flv_lcblock_octects(const struct seg6_flavors_info *finfo)
{
return finfo->lcblock_bits >> 3;
}
static __u8 seg6_flv_lcnode_func_octects(const struct seg6_flavors_info *finfo)
{
return finfo->lcnode_func_bits >> 3;
}
static bool seg6_next_csid_is_arg_zero(const struct in6_addr *addr,
const struct seg6_flavors_info *finfo)
{
__u8 fnc_octects = seg6_flv_lcnode_func_octects(finfo);
__u8 blk_octects = seg6_flv_lcblock_octects(finfo);
__u8 arg_octects;
int i;
arg_octects = 16 - blk_octects - fnc_octects;
for (i = 0; i < arg_octects; ++i) {
if (addr->s6_addr[blk_octects + fnc_octects + i] != 0x00)
return false;
}
return true;
}
/* assume that DA.Argument length > 0 */
static void seg6_next_csid_advance_arg(struct in6_addr *addr,
const struct seg6_flavors_info *finfo)
{
__u8 fnc_octects = seg6_flv_lcnode_func_octects(finfo);
__u8 blk_octects = seg6_flv_lcblock_octects(finfo);
/* advance DA.Argument */
memmove(&addr->s6_addr[blk_octects],
&addr->s6_addr[blk_octects + fnc_octects],
16 - blk_octects - fnc_octects);
memset(&addr->s6_addr[16 - fnc_octects], 0x00, fnc_octects);
}
static int input_action_end_core(struct sk_buff *skb,
struct seg6_local_lwt *slwt)
{
struct ipv6_sr_hdr *srh;
@ -291,6 +384,38 @@ drop:
return -EINVAL;
}
static int end_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_core(skb, slwt);
/* update DA */
seg6_next_csid_advance_arg(daddr, finfo);
seg6_lookup_nexthop(skb, NULL, 0);
return dst_input(skb);
}
static bool seg6_next_csid_enabled(__u32 fops)
{
return fops & BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID);
}
/* regular endpoint function */
static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
const struct seg6_flavors_info *finfo = &slwt->flv_info;
if (seg6_next_csid_enabled(finfo->flv_ops))
return end_next_csid_core(skb, slwt);
return input_action_end_core(skb, slwt);
}
/* regular endpoint, and forward to specified nexthop */
static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
@ -951,7 +1076,8 @@ static struct seg6_action_desc seg6_action_table[] = {
{
.action = SEG6_LOCAL_ACTION_END,
.attrs = 0,
.optattrs = SEG6_F_LOCAL_COUNTERS,
.optattrs = SEG6_F_LOCAL_COUNTERS |
SEG6_F_ATTR(SEG6_LOCAL_FLAVORS),
.input = input_action_end,
},
{
@ -1132,6 +1258,7 @@ static const struct nla_policy seg6_local_policy[SEG6_LOCAL_MAX + 1] = {
[SEG6_LOCAL_OIF] = { .type = NLA_U32 },
[SEG6_LOCAL_BPF] = { .type = NLA_NESTED },
[SEG6_LOCAL_COUNTERS] = { .type = NLA_NESTED },
[SEG6_LOCAL_FLAVORS] = { .type = NLA_NESTED },
};
static int parse_nla_srh(struct nlattr **attrs, struct seg6_local_lwt *slwt,
@ -1551,6 +1678,192 @@ static void destroy_attr_counters(struct seg6_local_lwt *slwt)
free_percpu(slwt->pcpu_counters);
}
static const
struct nla_policy seg6_local_flavors_policy[SEG6_LOCAL_FLV_MAX + 1] = {
[SEG6_LOCAL_FLV_OPERATION] = { .type = NLA_U32 },
[SEG6_LOCAL_FLV_LCBLOCK_BITS] = { .type = NLA_U8 },
[SEG6_LOCAL_FLV_LCNODE_FN_BITS] = { .type = NLA_U8 },
};
/* check whether the lengths of the Locator-Block and Locator-Node Function
* are compatible with the dimension of a C-SID container.
*/
static int seg6_chk_next_csid_cfg(__u8 block_len, __u8 func_len)
{
/* Locator-Block and Locator-Node Function cannot exceed 128 bits
* (i.e. C-SID container lenghts).
*/
if (next_csid_chk_cntr_bits(block_len, func_len))
return -EINVAL;
/* Locator-Block length must be greater than zero and evenly divisible
* by 8. There must be room for a Locator-Node Function, at least.
*/
if (next_csid_chk_lcblock_bits(block_len))
return -EINVAL;
/* Locator-Node Function length must be greater than zero and evenly
* divisible by 8. There must be room for the Locator-Block.
*/
if (next_csid_chk_lcnode_fn_bits(func_len))
return -EINVAL;
return 0;
}
static int seg6_parse_nla_next_csid_cfg(struct nlattr **tb,
struct seg6_flavors_info *finfo,
struct netlink_ext_ack *extack)
{
__u8 func_len = SEG6_LOCAL_LCNODE_FN_DBITS;
__u8 block_len = SEG6_LOCAL_LCBLOCK_DBITS;
int rc;
if (tb[SEG6_LOCAL_FLV_LCBLOCK_BITS])
block_len = nla_get_u8(tb[SEG6_LOCAL_FLV_LCBLOCK_BITS]);
if (tb[SEG6_LOCAL_FLV_LCNODE_FN_BITS])
func_len = nla_get_u8(tb[SEG6_LOCAL_FLV_LCNODE_FN_BITS]);
rc = seg6_chk_next_csid_cfg(block_len, func_len);
if (rc < 0) {
NL_SET_ERR_MSG(extack,
"Invalid Locator Block/Node Function lengths");
return rc;
}
finfo->lcblock_bits = block_len;
finfo->lcnode_func_bits = func_len;
return 0;
}
static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt,
struct netlink_ext_ack *extack)
{
struct seg6_flavors_info *finfo = &slwt->flv_info;
struct nlattr *tb[SEG6_LOCAL_FLV_MAX + 1];
unsigned long fops;
int rc;
rc = nla_parse_nested_deprecated(tb, SEG6_LOCAL_FLV_MAX,
attrs[SEG6_LOCAL_FLAVORS],
seg6_local_flavors_policy, NULL);
if (rc < 0)
return rc;
/* this attribute MUST always be present since it represents the Flavor
* operation(s) to be carried out.
*/
if (!tb[SEG6_LOCAL_FLV_OPERATION])
return -EINVAL;
fops = nla_get_u32(tb[SEG6_LOCAL_FLV_OPERATION]);
if (fops & ~SEG6_LOCAL_FLV_SUPP_OPS) {
NL_SET_ERR_MSG(extack, "Unsupported Flavor operation(s)");
return -EOPNOTSUPP;
}
finfo->flv_ops = fops;
if (seg6_next_csid_enabled(fops)) {
/* Locator-Block and Locator-Node Function lengths can be
* provided by the user space. Otherwise, default values are
* applied.
*/
rc = seg6_parse_nla_next_csid_cfg(tb, finfo, extack);
if (rc < 0)
return rc;
}
return 0;
}
static int seg6_fill_nla_next_csid_cfg(struct sk_buff *skb,
struct seg6_flavors_info *finfo)
{
if (nla_put_u8(skb, SEG6_LOCAL_FLV_LCBLOCK_BITS, finfo->lcblock_bits))
return -EMSGSIZE;
if (nla_put_u8(skb, SEG6_LOCAL_FLV_LCNODE_FN_BITS,
finfo->lcnode_func_bits))
return -EMSGSIZE;
return 0;
}
static int put_nla_flavors(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
struct seg6_flavors_info *finfo = &slwt->flv_info;
__u32 fops = finfo->flv_ops;
struct nlattr *nest;
int rc;
nest = nla_nest_start(skb, SEG6_LOCAL_FLAVORS);
if (!nest)
return -EMSGSIZE;
if (nla_put_u32(skb, SEG6_LOCAL_FLV_OPERATION, fops)) {
rc = -EMSGSIZE;
goto err;
}
if (seg6_next_csid_enabled(fops)) {
rc = seg6_fill_nla_next_csid_cfg(skb, finfo);
if (rc < 0)
goto err;
}
return nla_nest_end(skb, nest);
err:
nla_nest_cancel(skb, nest);
return rc;
}
static int seg6_cmp_nla_next_csid_cfg(struct seg6_flavors_info *finfo_a,
struct seg6_flavors_info *finfo_b)
{
if (finfo_a->lcblock_bits != finfo_b->lcblock_bits)
return 1;
if (finfo_a->lcnode_func_bits != finfo_b->lcnode_func_bits)
return 1;
return 0;
}
static int cmp_nla_flavors(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
struct seg6_flavors_info *finfo_a = &a->flv_info;
struct seg6_flavors_info *finfo_b = &b->flv_info;
if (finfo_a->flv_ops != finfo_b->flv_ops)
return 1;
if (seg6_next_csid_enabled(finfo_a->flv_ops)) {
if (seg6_cmp_nla_next_csid_cfg(finfo_a, finfo_b))
return 1;
}
return 0;
}
static int encap_size_flavors(struct seg6_local_lwt *slwt)
{
struct seg6_flavors_info *finfo = &slwt->flv_info;
int nlsize;
nlsize = nla_total_size(0) + /* nest SEG6_LOCAL_FLAVORS */
nla_total_size(4); /* SEG6_LOCAL_FLV_OPERATION */
if (seg6_next_csid_enabled(finfo->flv_ops))
nlsize += nla_total_size(1) + /* SEG6_LOCAL_FLV_LCBLOCK_BITS */
nla_total_size(1); /* SEG6_LOCAL_FLV_LCNODE_FN_BITS */
return nlsize;
}
struct seg6_action_param {
int (*parse)(struct nlattr **attrs, struct seg6_local_lwt *slwt,
struct netlink_ext_ack *extack);
@ -1603,6 +1916,10 @@ static struct seg6_action_param seg6_action_params[SEG6_LOCAL_MAX + 1] = {
.put = put_nla_counters,
.cmp = cmp_nla_counters,
.destroy = destroy_attr_counters },
[SEG6_LOCAL_FLAVORS] = { .parse = parse_nla_flavors,
.put = put_nla_flavors,
.cmp = cmp_nla_flavors },
};
/* call the destroy() callback (if available) for each set attribute in
@ -1916,6 +2233,9 @@ static int seg6_local_get_encap_size(struct lwtunnel_state *lwt)
/* SEG6_LOCAL_CNT_ERRORS */
nla_total_size_64bit(sizeof(__u64));
if (attrs & SEG6_F_ATTR(SEG6_LOCAL_FLAVORS))
nlsize += encap_size_flavors(slwt);
return nlsize;
}
@ -1971,6 +2291,15 @@ int __init seg6_local_init(void)
*/
BUILD_BUG_ON(SEG6_LOCAL_MAX + 1 > BITS_PER_TYPE(unsigned long));
/* If the default NEXT-C-SID Locator-Block/Node Function lengths (in
* bits) have been changed with invalid values, kernel build stops
* here.
*/
BUILD_BUG_ON(next_csid_chk_cntr_bits(SEG6_LOCAL_LCBLOCK_DBITS,
SEG6_LOCAL_LCNODE_FN_DBITS));
BUILD_BUG_ON(next_csid_chk_lcblock_bits(SEG6_LOCAL_LCBLOCK_DBITS));
BUILD_BUG_ON(next_csid_chk_lcnode_fn_bits(SEG6_LOCAL_LCNODE_FN_DBITS));
return lwtunnel_encap_add_ops(&seg6_local_ops,
LWTUNNEL_ENCAP_SEG6_LOCAL);
}