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Lockless hostentry resolution
Now the hostentry doesn't need to lock table, instead it tracks the hostentry version and retries if the hostentry changed while updating.
This commit is contained in:
Maria Matejka
parent
83a409abd2
commit
182a97f5e6
@ -502,9 +502,10 @@ struct hostentry {
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struct hostentry *next; /* Next in hash chain */
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unsigned hash_key; /* Hash key */
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u32 igp_metric; /* Chosen route IGP metric */
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_Atomic u32 version; /* Bumped on update */
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byte nexthop_linkable; /* Nexthop list is completely non-device */
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ea_list *src; /* Source attributes */
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struct lfuc uc; /* Use count */
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byte nexthop_linkable; /* Nexthop list is completely non-device */
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};
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struct hostcache {
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@ -669,6 +670,7 @@ struct rt_show_data_rtable * rt_show_add_table(struct rt_show_data *d, rtable *t
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/* Host entry: Resolve hook for recursive nexthops */
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extern struct ea_class ea_gen_hostentry;
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extern struct ea_class ea_gen_hostentry_version;
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struct hostentry_adata {
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adata ad;
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struct hostentry *he;
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@ -161,6 +161,13 @@ struct ea_class ea_gen_hostentry = {
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.freed = ea_gen_hostentry_freed,
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};
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struct ea_class ea_gen_hostentry_version = {
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.name = "hostentry version",
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.type = T_INT,
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.readonly = 1,
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.hidden = 1,
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};
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const char * rta_dest_names[RTD_MAX] = {
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[RTD_NONE] = "",
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[RTD_UNICAST] = "unicast",
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@ -1821,6 +1828,7 @@ rta_init(void)
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/* These attributes are required to be first for nice "show route" output */
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ea_register_init(&ea_gen_nexthop);
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ea_register_init(&ea_gen_hostentry);
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ea_register_init(&ea_gen_hostentry_version);
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/* Other generic route attributes */
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ea_register_init(&ea_gen_preference);
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228
nest/rt-table.c
228
nest/rt-table.c
@ -3001,139 +3001,143 @@ ea_set_hostentry(ea_list **to, rtable *dep, rtable *src, ip_addr gw, ip_addr ll,
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static void
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rta_apply_hostentry(struct rtable_private *tab UNUSED, ea_list **to, struct hostentry_adata *head)
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rta_apply_hostentry(ea_list **to, struct hostentry_adata *head)
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{
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struct hostentry *he = head->he;
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u32 *labels = head->labels;
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u32 lnum = (u32 *) (head->ad.data + head->ad.length) - labels;
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struct hostentry *he = head->he;
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ea_set_attr_u32(to, &ea_gen_igp_metric, 0, he->igp_metric);
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rcu_read_lock();
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u32 version = atomic_load_explicit(&he->version, memory_order_acquire);
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if (!he->src)
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while (1)
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{
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ea_set_dest(to, 0, RTD_UNREACHABLE);
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return;
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}
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eattr *he_nh_ea = ea_find(he->src, &ea_gen_nexthop);
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ASSERT_DIE(he_nh_ea);
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struct nexthop_adata *nhad = (struct nexthop_adata *) he_nh_ea->u.ptr;
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int idest = nhea_dest(he_nh_ea);
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if ((idest != RTD_UNICAST) ||
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!lnum && he->nexthop_linkable)
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{ /* Just link the nexthop chain, no label append happens. */
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ea_copy_attr(to, he->src, &ea_gen_nexthop);
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return;
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}
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uint total_size = OFFSETOF(struct nexthop_adata, nh);
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NEXTHOP_WALK(nh, nhad)
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{
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if (nh->labels + lnum > MPLS_MAX_LABEL_STACK)
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if (version & 1)
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{
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log(L_WARN "Sum of label stack sizes %d + %d = %d exceedes allowed maximum (%d)",
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nh->labels, lnum, nh->labels + lnum, MPLS_MAX_LABEL_STACK);
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rcu_read_unlock();
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birdloop_yield();
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rcu_read_lock();
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version = atomic_load_explicit(&he->version, memory_order_acquire);
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continue;
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}
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total_size += NEXTHOP_SIZE_CNT(nh->labels + lnum);
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}
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ea_set_attr_u32(to, &ea_gen_igp_metric, 0, he->igp_metric);
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if (total_size == OFFSETOF(struct nexthop_adata, nh))
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{
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log(L_WARN "No valid nexthop remaining, setting route unreachable");
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struct nexthop_adata nha = {
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.ad.length = NEXTHOP_DEST_SIZE,
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.dest = RTD_UNREACHABLE,
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};
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ea_set_attr_data(to, &ea_gen_nexthop, 0, &nha.ad.data, nha.ad.length);
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return;
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}
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struct nexthop_adata *new = (struct nexthop_adata *) tmp_alloc_adata(total_size);
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struct nexthop *dest = &new->nh;
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NEXTHOP_WALK(nh, nhad)
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{
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if (nh->labels + lnum > MPLS_MAX_LABEL_STACK)
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continue;
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memcpy(dest, nh, NEXTHOP_SIZE(nh));
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if (lnum)
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if (!he->src)
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{
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memcpy(&(dest->label[dest->labels]), labels, lnum * sizeof labels[0]);
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dest->labels += lnum;
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ea_set_dest(to, 0, RTD_UNREACHABLE);
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break;
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}
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if (ipa_nonzero(nh->gw))
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/* Router nexthop */
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dest->flags = (dest->flags & RNF_ONLINK);
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else if (!(nh->iface->flags & IF_MULTIACCESS) || (nh->iface->flags & IF_LOOPBACK))
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dest->gw = IPA_NONE; /* PtP link - no need for nexthop */
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else if (ipa_nonzero(he->link))
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dest->gw = he->link; /* Device nexthop with link-local address known */
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else
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dest->gw = he->addr; /* Device nexthop with link-local address unknown */
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eattr *he_nh_ea = ea_find(he->src, &ea_gen_nexthop);
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ASSERT_DIE(he_nh_ea);
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dest = NEXTHOP_NEXT(dest);
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struct nexthop_adata *nhad = (struct nexthop_adata *) he_nh_ea->u.ptr;
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int idest = nhea_dest(he_nh_ea);
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if ((idest != RTD_UNICAST) ||
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!lnum && he->nexthop_linkable)
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{
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/* Just link the nexthop chain, no label append happens. */
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ea_copy_attr(to, he->src, &ea_gen_nexthop);
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break;
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}
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uint total_size = OFFSETOF(struct nexthop_adata, nh);
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NEXTHOP_WALK(nh, nhad)
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{
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if (nh->labels + lnum > MPLS_MAX_LABEL_STACK)
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{
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log(L_WARN "Sum of label stack sizes %d + %d = %d exceedes allowed maximum (%d)",
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nh->labels, lnum, nh->labels + lnum, MPLS_MAX_LABEL_STACK);
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continue;
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}
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total_size += NEXTHOP_SIZE_CNT(nh->labels + lnum);
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}
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if (total_size == OFFSETOF(struct nexthop_adata, nh))
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{
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log(L_WARN "No valid nexthop remaining, setting route unreachable");
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struct nexthop_adata nha = {
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.ad.length = NEXTHOP_DEST_SIZE,
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.dest = RTD_UNREACHABLE,
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};
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ea_set_attr_data(to, &ea_gen_nexthop, 0, &nha.ad.data, nha.ad.length);
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break;
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}
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struct nexthop_adata *new = (struct nexthop_adata *) tmp_alloc_adata(total_size);
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struct nexthop *dest = &new->nh;
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NEXTHOP_WALK(nh, nhad)
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{
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if (nh->labels + lnum > MPLS_MAX_LABEL_STACK)
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continue;
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memcpy(dest, nh, NEXTHOP_SIZE(nh));
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if (lnum)
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{
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memcpy(&(dest->label[dest->labels]), labels, lnum * sizeof labels[0]);
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dest->labels += lnum;
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}
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if (ipa_nonzero(nh->gw))
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/* Router nexthop */
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dest->flags = (dest->flags & RNF_ONLINK);
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else if (!(nh->iface->flags & IF_MULTIACCESS) || (nh->iface->flags & IF_LOOPBACK))
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dest->gw = IPA_NONE; /* PtP link - no need for nexthop */
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else if (ipa_nonzero(he->link))
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dest->gw = he->link; /* Device nexthop with link-local address known */
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else
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dest->gw = he->addr; /* Device nexthop with link-local address unknown */
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dest = NEXTHOP_NEXT(dest);
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}
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/* Fix final length */
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new->ad.length = (void *) dest - (void *) new->ad.data;
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ea_set_attr(to, EA_LITERAL_DIRECT_ADATA(
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&ea_gen_nexthop, 0, &new->ad));
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/* Has the HE version changed? */
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u32 end_version = atomic_load_explicit(&he->version, memory_order_acquire);
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/* Stayed stable, we can finalize the route */
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if (end_version == version)
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break;
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/* No, retry once again */
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version = end_version;
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}
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/* Fix final length */
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new->ad.length = (void *) dest - (void *) new->ad.data;
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ea_set_attr(to, EA_LITERAL_DIRECT_ADATA(
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&ea_gen_nexthop, 0, &new->ad));
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}
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rcu_read_unlock();
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static inline struct hostentry_adata *
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rta_next_hop_outdated(ea_list *a)
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{
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/* First retrieve the hostentry */
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eattr *heea = ea_find(a, &ea_gen_hostentry);
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if (!heea)
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return NULL;
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struct hostentry_adata *head = (struct hostentry_adata *) heea->u.ptr;
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/* If no nexthop is present, we have to create one */
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eattr *a_nh_ea = ea_find(a, &ea_gen_nexthop);
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if (!a_nh_ea)
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return head;
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struct nexthop_adata *nhad = (struct nexthop_adata *) a_nh_ea->u.ptr;
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/* Shortcut for unresolvable hostentry */
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if (!head->he->src)
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return NEXTHOP_IS_REACHABLE(nhad) ? head : NULL;
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/* Comparing our nexthop with the hostentry nexthop */
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eattr *he_nh_ea = ea_find(head->he->src, &ea_gen_nexthop);
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return (
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(ea_get_int(a, &ea_gen_igp_metric, IGP_METRIC_UNKNOWN) != head->he->igp_metric) ||
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(!head->he->nexthop_linkable) ||
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(!he_nh_ea != !a_nh_ea) ||
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(he_nh_ea && a_nh_ea && !adata_same(he_nh_ea->u.ptr, a_nh_ea->u.ptr)))
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? head : NULL;
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ea_set_attr_u32(to, &ea_gen_hostentry_version, 0, version);
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}
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static inline int
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rt_next_hop_update_rte(const rte *old, rte *new)
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{
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struct hostentry_adata *head = rta_next_hop_outdated(old->attrs);
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if (!head)
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eattr *hev = ea_find(old->attrs, &ea_gen_hostentry_version);
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if (!hev)
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return 0;
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u32 last_version = hev->u.data;
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eattr *heea = ea_find(old->attrs, &ea_gen_hostentry);
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ASSERT_DIE(heea);
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struct hostentry_adata *head = (struct hostentry_adata *) heea->u.ptr;
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u32 current_version = atomic_load_explicit(&head->he->version, memory_order_acquire);
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if (current_version == last_version)
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return 0;
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/* Get the state of the route just before nexthop was resolved */
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*new = *old;
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new->attrs = ea_strip_to(new->attrs, BIT32_ALL(EALS_PREIMPORT, EALS_FILTERED));
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RT_LOCKED(head->he->owner, tab)
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rta_apply_hostentry(tab, &new->attrs, head);
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rta_apply_hostentry(&new->attrs, head);
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return 1;
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}
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@ -3144,10 +3148,7 @@ rt_next_hop_resolve_rte(rte *r)
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if (!heea)
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return;
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struct hostentry_adata *head = (struct hostentry_adata *) heea->u.ptr;
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RT_LOCKED(head->he->owner, tab)
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rta_apply_hostentry(tab, &r->attrs, head);
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rta_apply_hostentry(&r->attrs, (struct hostentry_adata *) heea->u.ptr);
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}
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#ifdef CONFIG_BGP
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@ -4374,6 +4375,9 @@ rt_update_hostentry(struct rtable_private *tab, struct hostentry *he)
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int direct = 0;
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int pxlen = 0;
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/* Signalize work in progress */
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ASSERT_DIE((atomic_fetch_add_explicit(&he->version, 1, memory_order_acq_rel) & 1) == 0);
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/* Reset the hostentry */
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he->src = NULL;
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he->nexthop_linkable = 0;
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@ -4426,6 +4430,10 @@ rt_update_hostentry(struct rtable_private *tab, struct hostentry *he)
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}
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done:
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/* Signalize work done and wait for readers */
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ASSERT_DIE((atomic_fetch_add_explicit(&he->version, 1, memory_order_acq_rel) & 1) == 1);
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synchronize_rcu();
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/* Add a prefix range to the trie */
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trie_add_prefix(tab->hostcache->trie, &he_addr, pxlen, he_addr.pxlen);
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