Merge pull request #13649 from donaldsharp/unlock_the_node_or_else

[mirror_frr.git] / isisd / isis_sr.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * This is an implementation of Segment Routing for IS-IS as per RFC 8667
 *
 * Copyright (C) 2019 Orange http://www.orange.com
 *
 * Author: Olivier Dugeon <olivier.dugeon@orange.com>
 * Contributor: Renato Westphal <renato@opensourcerouting.org> for NetDEF
 */

#include <zebra.h>

#include "if.h"
#include "linklist.h"
#include "log.h"
#include "command.h"
#include "termtable.h"
#include "memory.h"
#include "prefix.h"
#include "table.h"
#include "srcdest_table.h"
#include "vty.h"
#include "zclient.h"
#include "lib/lib_errors.h"

#include "isisd/isisd.h"
#include "isisd/isis_spf.h"
#include "isisd/isis_spf_private.h"
#include "isisd/isis_adjacency.h"
#include "isisd/isis_route.h"
#include "isisd/isis_mt.h"
#include "isisd/isis_sr.h"
#include "isisd/isis_tlvs.h"
#include "isisd/isis_misc.h"
#include "isisd/isis_zebra.h"
#include "isisd/isis_errors.h"

/* Local variables and functions */
DEFINE_MTYPE_STATIC(ISISD, ISIS_SR_INFO, "ISIS segment routing information");

static void sr_local_block_delete(struct isis_area *area);
static int sr_local_block_init(struct isis_area *area);
static void sr_adj_sid_update(struct sr_adjacency *sra,
                              struct sr_local_block *srlb);
static void sr_adj_sid_del(struct sr_adjacency *sra);

/* --- RB-Tree Management functions ----------------------------------------- */

/**
 * Configured SR Prefix comparison for RB-Tree.
 *
 * @param a     First SR prefix
 * @param b     Second SR prefix
 *
 * @return      -1 (a < b), 0 (a == b) or +1 (a > b)
 */
static inline int sr_prefix_sid_cfg_compare(const struct sr_prefix_cfg *a,
                                            const struct sr_prefix_cfg *b)
{
        int ret;

        ret = prefix_cmp(&a->prefix, &b->prefix);
        if (ret != 0)
                return ret;

        ret = a->algorithm - b->algorithm;
        if (ret != 0)
                return ret;

        return 0;
}
DECLARE_RBTREE_UNIQ(srdb_prefix_cfg, struct sr_prefix_cfg, entry,
                    sr_prefix_sid_cfg_compare);

/**
 * Find SRGB associated to a System ID.
 *
 * @param area  IS-IS LSP database
 * @param sysid System ID to lookup
 *
 * @return      Pointer to SRGB if found, NULL otherwise
 */
struct isis_sr_block *isis_sr_find_srgb(struct lspdb_head *lspdb,
                                        const uint8_t *sysid)
{
        struct isis_lsp *lsp;

        lsp = isis_root_system_lsp(lspdb, sysid);
        if (!lsp)
                return NULL;

        if (!lsp->tlvs->router_cap
            || lsp->tlvs->router_cap->srgb.range_size == 0)
                return NULL;

        return &lsp->tlvs->router_cap->srgb;
}

/**
 * Compute input label for the given Prefix-SID.
 *
 * @param area    IS-IS area
 * @param psid    IS-IS Prefix-SID Sub-TLV
 * @param local   Indicates whether the Prefix-SID is local or not
 *
 * @return      MPLS label or MPLS_INVALID_LABEL in case of SRGB overflow
 */
mpls_label_t sr_prefix_in_label(struct isis_area *area,
                                struct isis_prefix_sid *psid, bool local)
{
        /*
         * No need to assign a label for local Prefix-SIDs unless the no-PHP
         * flag is set.
         */
        if (local
            && (!CHECK_FLAG(psid->flags, ISIS_PREFIX_SID_NO_PHP)
                || CHECK_FLAG(psid->flags, ISIS_PREFIX_SID_EXPLICIT_NULL)))
                return MPLS_INVALID_LABEL;

        /* Return SID value as MPLS label if it is an Absolute SID */
        if (CHECK_FLAG(psid->flags,
                       ISIS_PREFIX_SID_VALUE | ISIS_PREFIX_SID_LOCAL))
                return psid->value;

        /* Check that SID index falls inside the SRGB */
        if (psid->value >= (area->srdb.config.srgb_upper_bound
                            - area->srdb.config.srgb_lower_bound + 1)) {
                flog_warn(EC_ISIS_SID_OVERFLOW,
                          "%s: SID index %u falls outside local SRGB range",
                          __func__, psid->value);
                return MPLS_INVALID_LABEL;
        }

        /* Return MPLS label as SID index + SRGB_lower_bound as per RFC 8667 */
        return (area->srdb.config.srgb_lower_bound + psid->value);
}

/**
 * Compute output label for the given Prefix-SID.
 *
 * @param lspdb         IS-IS LSP database
 * @param family        Prefix-SID address family
 * @param psid          Prefix-SID Sub-TLV
 * @param nh_sysid      System ID of the nexthop node
 * @param last_hop      Indicates whether the nexthop node is the last hop
 *
 * @return              MPLS label or MPLS_INVALID_LABEL in case of error
 */
mpls_label_t sr_prefix_out_label(struct lspdb_head *lspdb, int family,
                                 struct isis_prefix_sid *psid,
                                 const uint8_t *nh_sysid, bool last_hop)
{
        struct isis_sr_block *nh_srgb;

        if (last_hop) {
                if (!CHECK_FLAG(psid->flags, ISIS_PREFIX_SID_NO_PHP))
                        return MPLS_LABEL_IMPLICIT_NULL;

                if (CHECK_FLAG(psid->flags, ISIS_PREFIX_SID_EXPLICIT_NULL)) {
                        if (family == AF_INET)
                                return MPLS_LABEL_IPV4_EXPLICIT_NULL;
                        else
                                return MPLS_LABEL_IPV6_EXPLICIT_NULL;
                }
                /* Fallthrough */
        }

        /* Return SID value as MPLS label if it is an Absolute SID */
        if (CHECK_FLAG(psid->flags,
                       ISIS_PREFIX_SID_VALUE | ISIS_PREFIX_SID_LOCAL)) {
                /*
                 * V/L SIDs have local significance, so only adjacent routers
                 * can use them (RFC8667 section #2.1.1.1)
                 */
                if (!last_hop)
                        return MPLS_INVALID_LABEL;
                return psid->value;
        }

        /* Check that SID index falls inside the SRGB */
        nh_srgb = isis_sr_find_srgb(lspdb, nh_sysid);
        if (!nh_srgb)
                return MPLS_INVALID_LABEL;

        /*
         * Check if the nexthop can handle SR-MPLS encapsulated IPv4 or
         * IPv6 packets.
         */
        if ((family == AF_INET && !IS_SR_IPV4(nh_srgb))
            || (family == AF_INET6 && !IS_SR_IPV6(nh_srgb)))
                return MPLS_INVALID_LABEL;

        if (psid->value >= nh_srgb->range_size) {
                flog_warn(EC_ISIS_SID_OVERFLOW,
                          "%s: SID index %u falls outside remote SRGB range",
                          __func__, psid->value);
                return MPLS_INVALID_LABEL;
        }

        /* Return MPLS label as SID index + SRGB_lower_bound as per RFC 8667 */
        return (nh_srgb->lower_bound + psid->value);
}

/* --- Functions used for Yang model and CLI to configure Segment Routing --- */

/**
 * Check if prefix correspond to a Node SID.
 *
 * @param ifp     Interface
 * @param prefix  Prefix to be checked
 *
 * @return        True if the interface/address pair corresponds to a Node-SID
 */
static bool sr_prefix_is_node_sid(const struct interface *ifp,
                                  const struct prefix *prefix)
{
        return (if_is_loopback(ifp) && is_host_route(prefix));
}

/**
 * Update local SRGB configuration. SRGB is reserved though Label Manager.
 * This function trigger the update of local Prefix-SID installation.
 *
 * @param area          IS-IS area
 * @param lower_bound   Lower bound of SRGB
 * @param upper_bound   Upper bound of SRGB
 *
 * @return              0 on success, -1 otherwise
 */
int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
                            uint32_t upper_bound)
{
        struct isis_sr_db *srdb = &area->srdb;

        sr_debug("ISIS-Sr (%s): Update SRGB with new range [%u/%u]",
                 area->area_tag, lower_bound, upper_bound);

        /* Just store new SRGB values if Label Manager is not available.
         * SRGB will be configured later when SR start */
        if (!isis_zebra_label_manager_ready()) {
                srdb->config.srgb_lower_bound = lower_bound;
                srdb->config.srgb_upper_bound = upper_bound;
                return 0;
        }

        /* Label Manager is ready, start by releasing the old SRGB. */
        if (srdb->srgb_active) {
                isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
                                               srdb->config.srgb_upper_bound);
                srdb->srgb_active = false;
        }

        srdb->config.srgb_lower_bound = lower_bound;
        srdb->config.srgb_upper_bound = upper_bound;

        if (srdb->enabled) {
                /* then request new SRGB if SR is enabled. */
                if (isis_zebra_request_label_range(
                            srdb->config.srgb_lower_bound,
                            srdb->config.srgb_upper_bound
                                    - srdb->config.srgb_lower_bound + 1) < 0) {
                        srdb->srgb_active = false;
                        return -1;
                } else
                        srdb->srgb_active = true;


                sr_debug("  |- Got new SRGB [%u/%u]",
                         srdb->config.srgb_lower_bound,
                         srdb->config.srgb_upper_bound);

                lsp_regenerate_schedule(area, area->is_type, 0);
        } else if (srdb->config.enabled) {
                /* Try to enable SR again using the new SRGB. */
                isis_sr_start(area);
        }

        return 0;
}

/**
 * Update Segment Routing Local Block range which is reserved though the
 * Label Manager. This function trigger the update of local Adjacency-SID
 * installation.
 *
 * @param area          IS-IS area
 * @param lower_bound   Lower bound of SRLB
 * @param upper_bound   Upper bound of SRLB
 *
 * @return              0 on success, -1 otherwise
 */
int isis_sr_cfg_srlb_update(struct isis_area *area, uint32_t lower_bound,
                            uint32_t upper_bound)
{
        struct isis_sr_db *srdb = &area->srdb;
        struct listnode *node;
        struct sr_adjacency *sra;

        sr_debug("ISIS-Sr (%s): Update SRLB with new range [%u/%u]",
                 area->area_tag, lower_bound, upper_bound);

        /* Just store new SRLB values if Label Manager is not available.
         * SRLB will be configured later when SR start */
        if (!isis_zebra_label_manager_ready()) {
                srdb->config.srlb_lower_bound = lower_bound;
                srdb->config.srlb_upper_bound = upper_bound;
                return 0;
        }

        /* LM is ready, start by deleting the old SRLB */
        sr_local_block_delete(area);

        srdb->config.srlb_lower_bound = lower_bound;
        srdb->config.srlb_upper_bound = upper_bound;

        if (srdb->enabled) {
                /* Initialize new SRLB */
                if (sr_local_block_init(area) != 0)
                        return -1;

                /* Reinstall local Adjacency-SIDs with new labels. */
                for (ALL_LIST_ELEMENTS_RO(area->srdb.adj_sids, node, sra))
                        sr_adj_sid_update(sra, &srdb->srlb);

                /* Update and Flood LSP */
                lsp_regenerate_schedule(area, area->is_type, 0);
        } else if (srdb->config.enabled) {
                /* Try to enable SR again using the new SRLB. */
                isis_sr_start(area);
        }

        return 0;
}

/**
 * Add new Prefix-SID configuration to the SRDB.
 *
 * @param area    IS-IS area
 * @param prefix  Prefix to be added
 *
 * @return        Newly added Prefix-SID configuration structure
 */
struct sr_prefix_cfg *isis_sr_cfg_prefix_add(struct isis_area *area,
                                             const struct prefix *prefix,
                                             uint8_t algorithm)
{
        struct sr_prefix_cfg *pcfg;
        struct interface *ifp;

        sr_debug("ISIS-Sr (%s): Add local prefix %pFX", area->area_tag, prefix);

        pcfg = XCALLOC(MTYPE_ISIS_SR_INFO, sizeof(*pcfg));
        pcfg->prefix = *prefix;
        pcfg->area = area;
        pcfg->algorithm = algorithm;

        /* Pull defaults from the YANG module. */
        pcfg->sid_type = yang_get_default_enum(
                "%s/prefix-sid-map/prefix-sid/sid-value-type", ISIS_SR);
        pcfg->last_hop_behavior = yang_get_default_enum(
                "%s/prefix-sid-map/prefix-sid/last-hop-behavior", ISIS_SR);

        /* Mark as node Sid if the prefix is host and configured in loopback */
        ifp = if_lookup_prefix(prefix, VRF_DEFAULT);
        if (ifp && sr_prefix_is_node_sid(ifp, prefix))
                pcfg->node_sid = true;

        /* Save prefix-sid configuration. */
        srdb_prefix_cfg_add(&area->srdb.config.prefix_sids, pcfg);

        return pcfg;
}

/**
 * Removal of locally configured Prefix-SID.
 *
 * @param pcfg  Configured Prefix-SID
 */
void isis_sr_cfg_prefix_del(struct sr_prefix_cfg *pcfg)
{
        struct isis_area *area = pcfg->area;

        sr_debug("ISIS-Sr (%s): Delete local Prefix-SID %pFX %s %u",
                 area->area_tag, &pcfg->prefix,
                 pcfg->sid_type == SR_SID_VALUE_TYPE_INDEX ? "index" : "label",
                 pcfg->sid);

        srdb_prefix_cfg_del(&area->srdb.config.prefix_sids, pcfg);
        XFREE(MTYPE_ISIS_SR_INFO, pcfg);
}

/**
 * Lookup for Prefix-SID in the local configuration.
 *
 * @param area    IS-IS area
 * @param prefix  Prefix to lookup
 *
 * @return        Configured Prefix-SID structure if found, NULL otherwise
 */
struct sr_prefix_cfg *isis_sr_cfg_prefix_find(struct isis_area *area,
                                              union prefixconstptr prefix,
                                              uint8_t algorithm)
{
        struct sr_prefix_cfg pcfg = {};

        prefix_copy(&pcfg.prefix, prefix.p);
        pcfg.algorithm = algorithm;
        return srdb_prefix_cfg_find(&area->srdb.config.prefix_sids, &pcfg);
}

/**
 * Fill in Prefix-SID Sub-TLV according to the corresponding configuration.
 *
 * @param pcfg      Prefix-SID configuration
 * @param external  False if prefix is locally configured, true otherwise
 * @param psid      Prefix-SID sub-TLV to be updated
 */
void isis_sr_prefix_cfg2subtlv(const struct sr_prefix_cfg *pcfg, bool external,
                               struct isis_prefix_sid *psid)
{
        /* Set SID algorithm. */
        psid->algorithm = pcfg->algorithm;

        /* Set SID flags. */
        psid->flags = 0;
        switch (pcfg->last_hop_behavior) {
        case SR_LAST_HOP_BEHAVIOR_EXP_NULL:
                SET_FLAG(psid->flags, ISIS_PREFIX_SID_NO_PHP);
                SET_FLAG(psid->flags, ISIS_PREFIX_SID_EXPLICIT_NULL);
                break;
        case SR_LAST_HOP_BEHAVIOR_NO_PHP:
                SET_FLAG(psid->flags, ISIS_PREFIX_SID_NO_PHP);
                UNSET_FLAG(psid->flags, ISIS_PREFIX_SID_EXPLICIT_NULL);
                break;
        case SR_LAST_HOP_BEHAVIOR_PHP:
                UNSET_FLAG(psid->flags, ISIS_PREFIX_SID_NO_PHP);
                UNSET_FLAG(psid->flags, ISIS_PREFIX_SID_EXPLICIT_NULL);
                break;
        }
        if (external)
                SET_FLAG(psid->flags, ISIS_PREFIX_SID_READVERTISED);
        if (pcfg->node_sid && !pcfg->n_flag_clear)
                SET_FLAG(psid->flags, ISIS_PREFIX_SID_NODE);

        /* Set SID value. */
        psid->value = pcfg->sid;
        if (pcfg->sid_type == SR_SID_VALUE_TYPE_ABSOLUTE) {
                SET_FLAG(psid->flags, ISIS_PREFIX_SID_VALUE);
                SET_FLAG(psid->flags, ISIS_PREFIX_SID_LOCAL);
        }
}

/**
 * Delete all backup Adj-SIDs.
 *
 * @param area  IS-IS area
 * @param level IS-IS level
 */
void isis_area_delete_backup_adj_sids(struct isis_area *area, int level)
{
        struct sr_adjacency *sra;
        struct listnode *node, *nnode;

        for (ALL_LIST_ELEMENTS(area->srdb.adj_sids, node, nnode, sra))
                if (sra->type == ISIS_SR_LAN_BACKUP
                    && (sra->adj->level & level))
                        sr_adj_sid_del(sra);
}

/* --- Segment Routing Local Block management functions --------------------- */

/**
 * Initialize Segment Routing Local Block from SRDB configuration and reserve
 * block of bits to manage label allocation.
 *
 * @param area  IS-IS area
 */
static int sr_local_block_init(struct isis_area *area)
{
        struct isis_sr_db *srdb = &area->srdb;
        struct sr_local_block *srlb = &srdb->srlb;

        /* Check if SRLB is not already configured */
        if (srlb->active)
                return 0;

        /*
         * Request SRLB to the label manager. If the allocation fails, return
         * an error to disable SR until a new SRLB is successfully allocated.
         */
        if (isis_zebra_request_label_range(
                    srdb->config.srlb_lower_bound,
                    srdb->config.srlb_upper_bound
                            - srdb->config.srlb_lower_bound + 1)) {
                srlb->active = false;
                return -1;
        }

        sr_debug("ISIS-Sr (%s): Got new SRLB [%u/%u]", area->area_tag,
                 srdb->config.srlb_lower_bound, srdb->config.srlb_upper_bound);

        /* Initialize the SRLB */
        srlb->start = srdb->config.srlb_lower_bound;
        srlb->end = srdb->config.srlb_upper_bound;
        srlb->current = 0;
        /* Compute the needed Used Mark number and allocate them */
        srlb->max_block = (srlb->end - srlb->start + 1) / SRLB_BLOCK_SIZE;
        if (((srlb->end - srlb->start + 1) % SRLB_BLOCK_SIZE) != 0)
                srlb->max_block++;
        srlb->used_mark = XCALLOC(MTYPE_ISIS_SR_INFO,
                                  srlb->max_block * SRLB_BLOCK_SIZE);
        srlb->active = true;

        return 0;
}

/**
 * Remove Segment Routing Local Block.
 *
 * @param area  IS-IS area
 */
static void sr_local_block_delete(struct isis_area *area)
{
        struct isis_sr_db *srdb = &area->srdb;
        struct sr_local_block *srlb = &srdb->srlb;

        /* Check if SRLB is not already delete */
        if (!srlb->active)
                return;

        sr_debug("ISIS-Sr (%s): Remove SRLB [%u/%u]", area->area_tag,
                 srlb->start, srlb->end);

        /* First release the label block */
        isis_zebra_release_label_range(srdb->config.srlb_lower_bound,
                                       srdb->config.srlb_upper_bound);

        /* Then reset SRLB structure */
        if (srlb->used_mark != NULL)
                XFREE(MTYPE_ISIS_SR_INFO, srlb->used_mark);
        srlb->active = false;
}

/**
 * Request a label from the Segment Routing Local Block.
 *
 * @param srlb  Segment Routing Local Block
 *
 * @return      First available label on success or MPLS_INVALID_LABEL if the
 *              block of labels is full
 */
static mpls_label_t sr_local_block_request_label(struct sr_local_block *srlb)
{
        mpls_label_t label;
        uint32_t index;
        uint32_t pos;
        uint32_t size = srlb->end - srlb->start + 1;

        /* Check if we ran out of available labels */
        if (srlb->current >= size)
                return MPLS_INVALID_LABEL;

        /* Get first available label and mark it used */
        label = srlb->current + srlb->start;
        index = srlb->current / SRLB_BLOCK_SIZE;
        pos = 1ULL << (srlb->current % SRLB_BLOCK_SIZE);
        srlb->used_mark[index] |= pos;

        /* Jump to the next free position */
        srlb->current++;
        pos = srlb->current % SRLB_BLOCK_SIZE;
        while (srlb->current < size) {
                if (pos == 0)
                        index++;
                if (!((1ULL << pos) & srlb->used_mark[index]))
                        break;
                else {
                        srlb->current++;
                        pos = srlb->current % SRLB_BLOCK_SIZE;
                }
        }

        if (srlb->current == size)
                zlog_warn(
                        "SR: Warning, SRLB is depleted and next label request will fail");

        return label;
}

/**
 * Release label in the Segment Routing Local Block.
 *
 * @param srlb  Segment Routing Local Block
 * @param label Label to be release
 *
 * @return      0 on success or -1 if label falls outside SRLB
 */
static int sr_local_block_release_label(struct sr_local_block *srlb,
                                        mpls_label_t label)
{
        uint32_t index;
        uint32_t pos;

        /* Check that label falls inside the SRLB */
        if ((label < srlb->start) || (label > srlb->end)) {
                flog_warn(EC_ISIS_SID_OVERFLOW,
                        "%s: Returning label %u is outside SRLB [%u/%u]",
                        __func__, label, srlb->start, srlb->end);
                return -1;
        }

        index = (label - srlb->start) / SRLB_BLOCK_SIZE;
        pos = 1ULL << ((label - srlb->start) % SRLB_BLOCK_SIZE);
        srlb->used_mark[index] &= ~pos;
        /* Reset current to the first available position */
        for (index = 0; index < srlb->max_block; index++) {
                if (srlb->used_mark[index] != 0xFFFFFFFFFFFFFFFF) {
                        for (pos = 0; pos < SRLB_BLOCK_SIZE; pos++)
                                if (!((1ULL << pos) & srlb->used_mark[index])) {
                                        srlb->current =
                                                index * SRLB_BLOCK_SIZE + pos;
                                        break;
                                }
                        break;
                }
        }

        return 0;
}

/* --- Segment Routing Adjacency-SID management functions ------------------- */

/**
 * Add new local Adjacency-SID.
 *
 * @param adj      IS-IS Adjacency
 * @param family   Inet Family (IPv4 or IPv6)
 * @param backup   True to initialize backup Adjacency SID
 * @param nexthops List of backup nexthops (for backup Adj-SIDs only)
 */
void sr_adj_sid_add_single(struct isis_adjacency *adj, int family, bool backup,
                           struct list *nexthops)
{
        struct isis_circuit *circuit = adj->circuit;
        struct isis_area *area = circuit->area;
        struct sr_adjacency *sra;
        struct isis_adj_sid *adj_sid;
        struct isis_lan_adj_sid *ladj_sid;
        union g_addr nexthop = {};
        uint8_t flags;
        mpls_label_t input_label;

        sr_debug("ISIS-Sr (%s): Add %s Adjacency SID", area->area_tag,
                 backup ? "Backup" : "Primary");

        /* Determine nexthop IP address */
        switch (family) {
        case AF_INET:
                if (!circuit->ip_router || !adj->ipv4_address_count)
                        return;

                nexthop.ipv4 = adj->ipv4_addresses[0];
                break;
        case AF_INET6:
                if (!circuit->ipv6_router || !adj->ll_ipv6_count)
                        return;

                nexthop.ipv6 = adj->ll_ipv6_addrs[0];
                break;
        default:
                flog_err(EC_LIB_DEVELOPMENT,
                         "%s: unexpected address-family: %u", __func__, family);
                exit(1);
        }

        /* Prepare Segment Routing Adjacency as per RFC8667 section #2.2 */
        flags = EXT_SUBTLV_LINK_ADJ_SID_VFLG | EXT_SUBTLV_LINK_ADJ_SID_LFLG;
        if (family == AF_INET6)
                SET_FLAG(flags, EXT_SUBTLV_LINK_ADJ_SID_FFLG);
        if (backup)
                SET_FLAG(flags, EXT_SUBTLV_LINK_ADJ_SID_BFLG);

        /* Get a label from the SRLB for this Adjacency */
        input_label = sr_local_block_request_label(&area->srdb.srlb);
        if (input_label == MPLS_INVALID_LABEL)
                return;

        if (circuit->ext == NULL)
                circuit->ext = isis_alloc_ext_subtlvs();

        sra = XCALLOC(MTYPE_ISIS_SR_INFO, sizeof(*sra));
        sra->type = backup ? ISIS_SR_LAN_BACKUP : ISIS_SR_ADJ_NORMAL;
        sra->input_label = input_label;
        sra->nexthop.family = family;
        sra->nexthop.address = nexthop;

        if (backup && nexthops) {
                struct isis_vertex_adj *vadj;
                struct listnode *node;

                sra->backup_nexthops = list_new();
                for (ALL_LIST_ELEMENTS_RO(nexthops, node, vadj)) {
                        struct isis_adjacency *adj = vadj->sadj->adj;
                        struct mpls_label_stack *label_stack;

                        label_stack = vadj->label_stack;
                        adjinfo2nexthop(family, sra->backup_nexthops, adj, NULL,
                                        label_stack);
                }
        }

        switch (circuit->circ_type) {
        /* LAN Adjacency-SID for Broadcast interface section #2.2.2 */
        case CIRCUIT_T_BROADCAST:
                ladj_sid = XCALLOC(MTYPE_ISIS_SUBTLV, sizeof(*ladj_sid));
                ladj_sid->family = family;
                ladj_sid->flags = flags;
                ladj_sid->weight = 0;
                memcpy(ladj_sid->neighbor_id, adj->sysid,
                       sizeof(ladj_sid->neighbor_id));
                ladj_sid->sid = input_label;
                isis_tlvs_add_lan_adj_sid(circuit->ext, ladj_sid);
                sra->u.ladj_sid = ladj_sid;
                break;
        /* Adjacency-SID for Point to Point interface section #2.2.1 */
        case CIRCUIT_T_P2P:
                adj_sid = XCALLOC(MTYPE_ISIS_SUBTLV, sizeof(*adj_sid));
                adj_sid->family = family;
                adj_sid->flags = flags;
                adj_sid->weight = 0;
                adj_sid->sid = input_label;
                isis_tlvs_add_adj_sid(circuit->ext, adj_sid);
                sra->u.adj_sid = adj_sid;
                break;
        default:
                flog_err(EC_LIB_DEVELOPMENT, "%s: unexpected circuit type: %u",
                         __func__, circuit->circ_type);
                exit(1);
        }

        /* Add Adjacency-SID in SRDB */
        sra->adj = adj;
        listnode_add(area->srdb.adj_sids, sra);
        listnode_add(adj->adj_sids, sra);

        isis_zebra_send_adjacency_sid(ZEBRA_MPLS_LABELS_ADD, sra);
}

/**
 * Add Primary and Backup local Adjacency SID.
 *
 * @param adj     IS-IS Adjacency
 * @param family  Inet Family (IPv4 or IPv6)
 */
static void sr_adj_sid_add(struct isis_adjacency *adj, int family)
{
        sr_adj_sid_add_single(adj, family, false, NULL);
}

static void sr_adj_sid_update(struct sr_adjacency *sra,
                              struct sr_local_block *srlb)
{
        struct isis_circuit *circuit = sra->adj->circuit;

        /* First remove the old MPLS Label */
        isis_zebra_send_adjacency_sid(ZEBRA_MPLS_LABELS_DELETE, sra);

        /* Got new label in the new SRLB */
        sra->input_label = sr_local_block_request_label(srlb);
        if (sra->input_label == MPLS_INVALID_LABEL)
                return;

        switch (circuit->circ_type) {
        case CIRCUIT_T_BROADCAST:
                sra->u.ladj_sid->sid = sra->input_label;
                break;
        case CIRCUIT_T_P2P:
                sra->u.adj_sid->sid = sra->input_label;
                break;
        default:
                flog_warn(EC_LIB_DEVELOPMENT, "%s: unexpected circuit type: %u",
                          __func__, circuit->circ_type);
                break;
        }

        /* Finally configure the new MPLS Label */
        isis_zebra_send_adjacency_sid(ZEBRA_MPLS_LABELS_ADD, sra);
}

/**
 * Delete local Adj-SID.
 *
 * @param sra   Segment Routing Adjacency
 */
static void sr_adj_sid_del(struct sr_adjacency *sra)
{
        struct isis_circuit *circuit = sra->adj->circuit;
        struct isis_area *area = circuit->area;

        sr_debug("ISIS-Sr (%s): Delete Adjacency SID", area->area_tag);

        isis_zebra_send_adjacency_sid(ZEBRA_MPLS_LABELS_DELETE, sra);

        /* Release dynamic label and remove subTLVs */
        switch (circuit->circ_type) {
        case CIRCUIT_T_BROADCAST:
                sr_local_block_release_label(&area->srdb.srlb,
                                             sra->u.ladj_sid->sid);
                isis_tlvs_del_lan_adj_sid(circuit->ext, sra->u.ladj_sid);
                break;
        case CIRCUIT_T_P2P:
                sr_local_block_release_label(&area->srdb.srlb,
                                             sra->u.adj_sid->sid);
                isis_tlvs_del_adj_sid(circuit->ext, sra->u.adj_sid);
                break;
        default:
                flog_err(EC_LIB_DEVELOPMENT, "%s: unexpected circuit type: %u",
                         __func__, circuit->circ_type);
                exit(1);
        }

        if (sra->type == ISIS_SR_LAN_BACKUP && sra->backup_nexthops) {
                sra->backup_nexthops->del =
                        (void (*)(void *))isis_nexthop_delete;
                list_delete(&sra->backup_nexthops);
        }

        /* Remove Adjacency-SID from the SRDB */
        listnode_delete(area->srdb.adj_sids, sra);
        listnode_delete(sra->adj->adj_sids, sra);
        XFREE(MTYPE_ISIS_SR_INFO, sra);
}

/**
 * Lookup Segment Routing Adj-SID by family and type.
 *
 * @param adj     IS-IS Adjacency
 * @param family  Inet Family (IPv4 or IPv6)
 * @param type    Adjacency SID type
 */
struct sr_adjacency *isis_sr_adj_sid_find(struct isis_adjacency *adj,
                                          int family, enum sr_adj_type type)
{
        struct sr_adjacency *sra;
        struct listnode *node;

        for (ALL_LIST_ELEMENTS_RO(adj->adj_sids, node, sra))
                if (sra->nexthop.family == family && sra->type == type)
                        return sra;

        return NULL;
}

/**
 * Remove all Adjacency-SIDs associated to an adjacency that is going down.
 *
 * @param adj   IS-IS Adjacency
 *
 * @return      0
 */
static int sr_adj_state_change(struct isis_adjacency *adj)
{
        struct sr_adjacency *sra;
        struct listnode *node, *nnode;

        if (!adj->circuit->area->srdb.enabled)
                return 0;

        if (adj->adj_state == ISIS_ADJ_UP)
                return 0;

        for (ALL_LIST_ELEMENTS(adj->adj_sids, node, nnode, sra))
                sr_adj_sid_del(sra);

        return 0;
}

/**
 * When IS-IS Adjacency got one or more IPv4/IPv6 addresses, add new IPv4 or
 * IPv6 address to corresponding Adjacency-SID accordingly.
 *
 * @param adj     IS-IS Adjacency
 * @param family  Inet Family (IPv4 or IPv6)
 * @param global  Indicate if it concerns the Local or Global IPv6 addresses
 *
 * @return        0
 */
static int sr_adj_ip_enabled(struct isis_adjacency *adj, int family,
                             bool global)
{
        if (!adj->circuit->area->srdb.enabled || global)
                return 0;

        sr_adj_sid_add(adj, family);

        return 0;
}

/**
 * When IS-IS Adjacency doesn't have any IPv4 or IPv6 addresses anymore,
 * delete the corresponding Adjacency-SID(s) accordingly.
 *
 * @param adj     IS-IS Adjacency
 * @param family  Inet Family (IPv4 or IPv6)
 * @param global  Indicate if it concerns the Local or Global IPv6 addresses
 *
 * @return        0
 */
static int sr_adj_ip_disabled(struct isis_adjacency *adj, int family,
                              bool global)
{
        struct sr_adjacency *sra;
        struct listnode *node, *nnode;

        if (!adj->circuit->area->srdb.enabled || global)
                return 0;

        for (ALL_LIST_ELEMENTS(adj->adj_sids, node, nnode, sra))
                if (sra->nexthop.family == family)
                        sr_adj_sid_del(sra);

        return 0;
}

/**
 * Activate local Prefix-SID when loopback interface goes up for IS-IS.
 *
 * @param ifp   Loopback Interface
 *
 * @return      0
 */
static int sr_if_new_hook(struct interface *ifp)
{
        struct sr_prefix_cfg *pcfgs[SR_ALGORITHM_COUNT] = {NULL};
        struct isis_circuit *circuit;
        struct isis_area *area;
        struct connected *connected;
        struct listnode *node;
        bool need_lsp_regenerate = false;

        /* Get corresponding circuit */
        circuit = circuit_scan_by_ifp(ifp);
        if (!circuit)
                return 0;

        area = circuit->area;
        if (!area)
                return 0;

        /*
         * Update the Node-SID flag of the configured Prefix-SID mappings if
         * necessary. This needs to be done here since isisd reads the startup
         * configuration before receiving interface information from zebra.
         */
        FOR_ALL_INTERFACES_ADDRESSES (ifp, connected, node) {

                for (int i = 0; i < SR_ALGORITHM_COUNT; i++) {
                        pcfgs[i] = isis_sr_cfg_prefix_find(
                                area, connected->address, i);

                        if (!pcfgs[i])
                                continue;

                        if (sr_prefix_is_node_sid(ifp, &pcfgs[i]->prefix)) {
                                pcfgs[i]->node_sid = true;
                                need_lsp_regenerate = true;
                        }
                }
        }

        if (need_lsp_regenerate)
                lsp_regenerate_schedule(area, area->is_type, 0);

        return 0;
}

/**
 * Show LFIB operation in human readable format.
 *
 * @param buf         Buffer to store string output. Must be pre-allocate
 * @param size        Size of the buffer
 * @param label_in    Input Label
 * @param label_out   Output Label
 *
 * @return           String containing LFIB operation in human readable format
 */
char *sr_op2str(char *buf, size_t size, mpls_label_t label_in,
                mpls_label_t label_out)
{
        if (size < 24)
                return NULL;

        if (label_in == MPLS_INVALID_LABEL) {
                snprintf(buf, size, "no-op.");
                return buf;
        }

        switch (label_out) {
        case MPLS_LABEL_IMPLICIT_NULL:
                snprintf(buf, size, "Pop(%u)", label_in);
                break;
        case MPLS_LABEL_IPV4_EXPLICIT_NULL:
        case MPLS_LABEL_IPV6_EXPLICIT_NULL:
                snprintf(buf, size, "Swap(%u, null)", label_in);
                break;
        case MPLS_INVALID_LABEL:
                snprintf(buf, size, "no-op.");
                break;
        default:
                snprintf(buf, size, "Swap(%u, %u)", label_in, label_out);
                break;
        }
        return buf;
}

/**
 * Show Segment Routing Node.
 *
 * @param vty   VTY output
 * @param area  IS-IS area
 * @param level IS-IS level
 */
static void show_node(struct vty *vty, struct isis_area *area, int level,
                      uint8_t algo)
{
        struct isis_lsp *lsp;
        struct ttable *tt;
        char buf[128];

        vty_out(vty, " IS-IS %s SR-Nodes:\n\n", circuit_t2string(level));

        /* Prepare table. */
        tt = ttable_new(&ttable_styles[TTSTYLE_BLANK]);
        ttable_add_row(tt, "System ID|SRGB|SRLB|Algorithm|MSD");
        tt->style.cell.rpad = 2;
        tt->style.corner = '+';
        ttable_restyle(tt);
        ttable_rowseps(tt, 0, BOTTOM, true, '-');

        frr_each (lspdb, &area->lspdb[level - 1], lsp) {
                struct isis_router_cap *cap;

                if (!lsp->tlvs)
                        continue;
                cap = lsp->tlvs->router_cap;
                if (!cap)
                        continue;
                if (cap->algo[algo] == SR_ALGORITHM_UNSET)
                        continue;

                if (cap->algo[algo] == SR_ALGORITHM_SPF)
                        snprintf(buf, sizeof(buf), "SPF");
                else if (cap->algo[algo] == SR_ALGORITHM_STRICT_SPF)
                        snprintf(buf, sizeof(buf), "S-SPF");
#ifndef FABRICD
                else
                        snprintf(buf, sizeof(buf), "Flex-Algo %d", algo);
#endif /* ifndef FABRICD */

                ttable_add_row(tt, "%pSY|%u - %u|%u - %u|%s|%u",
                               lsp->hdr.lsp_id, cap->srgb.lower_bound,
                               cap->srgb.lower_bound + cap->srgb.range_size - 1,
                               cap->srlb.lower_bound,
                               cap->srlb.lower_bound + cap->srlb.range_size - 1,
                               buf, cap->msd);
        }

        /* Dump the generated table. */
        if (tt->nrows > 1) {
                char *table;

                table = ttable_dump(tt, "\n");
                vty_out(vty, "%s\n", table);
                XFREE(MTYPE_TMP, table);
        }
        ttable_del(tt);
}

DEFUN(show_sr_node, show_sr_node_cmd,
      "show " PROTO_NAME
      " segment-routing node"
#ifndef FABRICD
      " [algorithm (128-255)]"
#endif /* ifndef FABRICD */
      ,
      SHOW_STR PROTO_HELP
      "Segment-Routing\n"
      "Segment-Routing node\n"
#ifndef FABRICD
      "Show Flex-algo nodes\n"
      "Algorithm number\n"
#endif /* ifndef FABRICD */
)
{
        struct listnode *node, *inode;
        struct isis_area *area;
        uint8_t algorithm = SR_ALGORITHM_SPF;
        struct isis *isis;
#ifndef FABRICD
        int idx = 0;

        if (argv_find(argv, argc, "algorithm", &idx))
                algorithm = (uint8_t)strtoul(argv[idx + 1]->arg, NULL, 10);
#endif /* ifndef FABRICD */

        for (ALL_LIST_ELEMENTS_RO(im->isis, inode, isis)) {
                for (ALL_LIST_ELEMENTS_RO(isis->area_list, node, area)) {
                        vty_out(vty, "Area %s:\n",
                                area->area_tag ? area->area_tag : "null");
                        if (!area->srdb.enabled) {
                                vty_out(vty, " Segment Routing is disabled\n");
                                continue;
                        }
                        for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS;
                             level++)
                                show_node(vty, area, level, algorithm);
                }
        }

        return CMD_SUCCESS;
}

/* --- IS-IS Segment Routing Management function ---------------------------- */

/**
 * Thread function to re-attempt connection to the Label Manager and thus be
 * able to start Segment Routing.
 *
 * @param start         Thread structure that contains area as argument
 *
 * @return              1 on success
 */
static void sr_start_label_manager(struct event *start)
{
        struct isis_area *area;

        area = EVENT_ARG(start);

        /* re-attempt to start SR & Label Manager connection */
        isis_sr_start(area);
}

/**
 * Enable SR on the given IS-IS area.
 *
 * @param area  IS-IS area
 *
 * @return      0 on success, -1 otherwise
 */
int isis_sr_start(struct isis_area *area)
{
        struct isis_sr_db *srdb = &area->srdb;
        struct isis_adjacency *adj;
        struct listnode *node;

        /* First start Label Manager if not ready */
        if (!isis_zebra_label_manager_ready())
                if (isis_zebra_label_manager_connect() < 0) {
                        /* Re-attempt to connect to Label Manager in 1 sec. */
                        event_add_timer(master, sr_start_label_manager, area, 1,
                                        &srdb->t_start_lm);
                        return -1;
                }

        /* Label Manager is ready, initialize the SRLB */
        if (sr_local_block_init(area) < 0)
                return -1;

        /*
         * Request SGRB to the label manager if not already active. If the
         * allocation fails, return an error to disable SR until a new SRGB
         * is successfully allocated.
         */
        if (!srdb->srgb_active) {
                if (isis_zebra_request_label_range(
                            srdb->config.srgb_lower_bound,
                            srdb->config.srgb_upper_bound
                                    - srdb->config.srgb_lower_bound + 1)
                    < 0) {
                        srdb->srgb_active = false;
                        return -1;
                } else
                        srdb->srgb_active = true;
        }

        sr_debug("ISIS-Sr: Starting Segment Routing for area %s",
                 area->area_tag);

        /* Create Adjacency-SIDs from existing IS-IS Adjacencies. */
        for (ALL_LIST_ELEMENTS_RO(area->adjacency_list, node, adj)) {
                if (adj->ipv4_address_count > 0)
                        sr_adj_sid_add(adj, AF_INET);
                if (adj->ll_ipv6_count > 0)
                        sr_adj_sid_add(adj, AF_INET6);
        }

        area->srdb.enabled = true;

        /* Regenerate LSPs to advertise Segment Routing capabilities. */
        lsp_regenerate_schedule(area, area->is_type, 0);

        return 0;
}

/**
 * Disable SR on the given IS-IS area.
 *
 * @param area  IS-IS area
 */
void isis_sr_stop(struct isis_area *area)
{
        struct isis_sr_db *srdb = &area->srdb;
        struct sr_adjacency *sra;
        struct listnode *node, *nnode;

        sr_debug("ISIS-Sr: Stopping Segment Routing for area %s",
                 area->area_tag);

        /* Disable any re-attempt to connect to Label Manager */
        EVENT_OFF(srdb->t_start_lm);

        /* Uninstall all local Adjacency-SIDs. */
        for (ALL_LIST_ELEMENTS(area->srdb.adj_sids, node, nnode, sra))
                sr_adj_sid_del(sra);

        /* Release SRGB if active. */
        if (srdb->srgb_active) {
                isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
                                               srdb->config.srgb_upper_bound);
                srdb->srgb_active = false;
        }

        /* Delete SRLB */
        sr_local_block_delete(area);

        area->srdb.enabled = false;

        /* Regenerate LSPs to advertise that the Node is no more SR enable. */
        lsp_regenerate_schedule(area, area->is_type, 0);
}

/**
 * IS-IS Segment Routing initialization for given area.
 *
 * @param area  IS-IS area
 */
void isis_sr_area_init(struct isis_area *area)
{
        struct isis_sr_db *srdb = &area->srdb;

        sr_debug("ISIS-Sr (%s): Initialize Segment Routing SRDB",
                 area->area_tag);

        /* Initialize Segment Routing Data Base */
        memset(srdb, 0, sizeof(*srdb));
        srdb->adj_sids = list_new();

        /* Pull defaults from the YANG module. */
#ifndef FABRICD
        srdb->config.enabled = yang_get_default_bool("%s/enabled", ISIS_SR);
        srdb->config.srgb_lower_bound = yang_get_default_uint32(
                "%s/label-blocks/srgb/lower-bound", ISIS_SR);
        srdb->config.srgb_upper_bound = yang_get_default_uint32(
                "%s/label-blocks/srgb/upper-bound", ISIS_SR);
        srdb->config.srlb_lower_bound = yang_get_default_uint32(
                "%s/label-blocks/srlb/lower-bound", ISIS_SR);
        srdb->config.srlb_upper_bound = yang_get_default_uint32(
                "%s/label-blocks/srlb/upper-bound", ISIS_SR);
#else
        srdb->config.enabled = false;
        srdb->config.srgb_lower_bound = SRGB_LOWER_BOUND;
        srdb->config.srgb_upper_bound = SRGB_UPPER_BOUND;
        srdb->config.srlb_lower_bound = SRLB_LOWER_BOUND;
        srdb->config.srlb_upper_bound = SRLB_UPPER_BOUND;
#endif
        srdb->config.msd = 0;
        srdb_prefix_cfg_init(&srdb->config.prefix_sids);
}

/**
 * Terminate IS-IS Segment Routing for the given area.
 *
 * @param area  IS-IS area
 */
void isis_sr_area_term(struct isis_area *area)
{
        struct isis_sr_db *srdb = &area->srdb;

        /* Stop Segment Routing */
        if (area->srdb.enabled)
                isis_sr_stop(area);

        /* Free Adjacency SID list */
        list_delete(&srdb->adj_sids);

        /* Clear Prefix-SID configuration. */
        while (srdb_prefix_cfg_count(&srdb->config.prefix_sids) > 0) {
                struct sr_prefix_cfg *pcfg;

                pcfg = srdb_prefix_cfg_first(&srdb->config.prefix_sids);
                isis_sr_cfg_prefix_del(pcfg);
        }
}

/**
 * IS-IS Segment Routing global initialization.
 */
void isis_sr_init(void)
{
        install_element(VIEW_NODE, &show_sr_node_cmd);

        /* Register hooks. */
        hook_register(isis_adj_state_change_hook, sr_adj_state_change);
        hook_register(isis_adj_ip_enabled_hook, sr_adj_ip_enabled);
        hook_register(isis_adj_ip_disabled_hook, sr_adj_ip_disabled);
        hook_register(isis_if_new_hook, sr_if_new_hook);
}

/**
 * IS-IS Segment Routing global terminate.
 */
void isis_sr_term(void)
{
        /* Unregister hooks. */
        hook_unregister(isis_adj_state_change_hook, sr_adj_state_change);
        hook_unregister(isis_adj_ip_enabled_hook, sr_adj_ip_enabled);
        hook_unregister(isis_adj_ip_disabled_hook, sr_adj_ip_disabled);
        hook_unregister(isis_if_new_hook, sr_if_new_hook);
}