[PATCH v5 net-next 2/3] net/ipv6: multipath routing: configurable seed

Balaev Pavel
2021-04-27T15:37:59Z

Ability for a user to assign seed value to IPv6 multipath route hashes.
This patch adds sysctl variable: net.ipv6.fib_multipath_hash_seed.

Signed-off-by: Balaev Pavel <balaevpa@infotecs.ru>
---
include/net/netns/ipv6.h | 3 ++
net/ipv6/route.c | 10 +++-
net/ipv6/sysctl_net_ipv6.c | 96 ++++++++++++++++++++++++++++++++++++++
3 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 808f0f79e..6bb383b0a 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -8,6 +8,7 @@
#ifndef __NETNS_IPV6_H__
#define __NETNS_IPV6_H__
#include <net/dst_ops.h>
+#include <linux/siphash.h>
#include <uapi/linux/icmpv6.h>

struct ctl_table_header;
@@ -30,6 +31,7 @@ struct netns_sysctl_ipv6 {
int ip6_rt_min_advmss;
u8 bindv6only;
u8 multipath_hash_policy;
+ u8 multipath_hash_seed;
u8 flowlabel_consistency;
u8 auto_flowlabels;
int icmpv6_time;
@@ -107,6 +109,7 @@ struct netns_ipv6 {
struct fib_rules_ops *mr6_rules_ops;
#endif
#endif
+ siphash_key_t __rcu *multipath_hash_seed_ctx;
atomic_t dev_addr_genid;
atomic_t fib6_sernum;
struct seg6_pernet_data *seg6_data;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 28801ae80..70c488812 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2331,6 +2331,7 @@ u32 rt6_multipath_hash(const struct net *net, const struct flowi6 *fl6,
const struct sk_buff *skb, struct flow_keys *flkeys)
{
struct flow_keys hash_keys;
+ siphash_key_t *seed_ctx;
u32 mhash;

switch (ip6_multipath_hash_policy(net)) {
@@ -2414,7 +2415,14 @@ u32 rt6_multipath_hash(const struct net *net, const struct flowi6 *fl6,
}
break;
}
- mhash = flow_hash_from_keys(&hash_keys);
+
+ rcu_read_lock();
+ seed_ctx = rcu_dereference(net->ipv6.multipath_hash_seed_ctx);
+ if (seed_ctx)
+ mhash = flow_multipath_hash_from_keys(&hash_keys, seed_ctx);
+ else
+ mhash = flow_hash_from_keys(&hash_keys);
+ rcu_read_unlock();

return mhash >> 1;
}
diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c
index 27102c3d6..349251cb7 100644
--- a/net/ipv6/sysctl_net_ipv6.c
+++ b/net/ipv6/sysctl_net_ipv6.c
@@ -40,6 +40,94 @@ static int proc_rt6_multipath_hash_policy(struct ctl_table *table, int write,
return ret;
}

+#define RT6_MULTIPATH_SEED_KEY_LENGTH sizeof(siphash_key_t)
+#define RT6_MULTIPATH_SEED_RANDOM "random"
+static int proc_rt6_multipath_hash_seed(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct net *net = container_of(table->data, struct net,
+ ipv6.sysctl.multipath_hash_seed);
+ /* maxlen to print the keys in hex (*2) and a comma in between keys. */
+ struct ctl_table tbl = {
+ .maxlen = ((RT6_MULTIPATH_SEED_KEY_LENGTH * 2) + 2)
+ };
+ siphash_key_t user_key, *ctx;
+ __le64 key[2];
+ int ret;
+
+ tbl.data = kmalloc(tbl.maxlen, GFP_KERNEL);
+
+ if (!tbl.data)
+ return -ENOMEM;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(net->ipv6.multipath_hash_seed_ctx);
+ if (ctx) {
+ put_unaligned_le64(ctx->key[0], &key[0]);
+ put_unaligned_le64(ctx->key[1], &key[1]);
+ user_key.key[0] = le64_to_cpu(key[0]);
+ user_key.key[1] = le64_to_cpu(key[1]);
+
+ snprintf(tbl.data, tbl.maxlen, "%016llx,%016llx",
+ user_key.key[0], user_key.key[1]);
+ } else {
+ snprintf(tbl.data, tbl.maxlen, "%s", RT6_MULTIPATH_SEED_RANDOM);
+ }
+ rcu_read_unlock();
+
+ ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+
+ if (write && ret == 0) {
+ siphash_key_t *new_ctx, *old_ctx;
+
+ if (!strcmp(tbl.data, RT6_MULTIPATH_SEED_RANDOM)) {
+ rtnl_lock();
+ old_ctx = rtnl_dereference(net->ipv6.multipath_hash_seed_ctx);
+ RCU_INIT_POINTER(net->ipv6.multipath_hash_seed_ctx, NULL);
+ rtnl_unlock();
+ if (old_ctx) {
+ synchronize_net();
+ kfree_sensitive(old_ctx);
+ }
+
+ pr_debug("multipath hash seed set to random value\n");
+ goto out;
+ }
+
+ if (sscanf(tbl.data, "%llx,%llx", user_key.key, user_key.key + 1) != 2) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ key[0] = cpu_to_le64(user_key.key[0]);
+ key[1] = cpu_to_le64(user_key.key[1]);
+ pr_debug("multipath hash seed set to 0x%llx,0x%llx\n",
+ user_key.key[0], user_key.key[1]);
+
+ new_ctx = kmalloc(sizeof(*new_ctx), GFP_KERNEL);
+ if (!new_ctx) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ new_ctx->key[0] = get_unaligned_le64(&key[0]);
+ new_ctx->key[1] = get_unaligned_le64(&key[1]);
+
+ rtnl_lock();
+ old_ctx = rtnl_dereference(net->ipv6.multipath_hash_seed_ctx);
+ rcu_assign_pointer(net->ipv6.multipath_hash_seed_ctx, new_ctx);
+ rtnl_unlock();
+ if (old_ctx) {
+ synchronize_net();
+ kfree_sensitive(old_ctx);
+ }
+ }
+
+out:
+ kfree(tbl.data);
+ return ret;
+}
+
static struct ctl_table ipv6_table_template[] = {
{
.procname = "bindv6only",
@@ -151,6 +239,14 @@ static struct ctl_table ipv6_table_template[] = {
.extra1 = SYSCTL_ZERO,
.extra2 = &two,
},
+ {
+ .procname = "fib_multipath_hash_seed",
+ .data = &init_net.ipv6.sysctl.multipath_hash_seed,
+ /* maxlen to print the keys in hex (*2) and a comma in between keys. */
+ .maxlen = (RT6_MULTIPATH_SEED_KEY_LENGTH * 2) + 2,
+ .mode = 0600,
+ .proc_handler = proc_rt6_multipath_hash_seed,
+ },
{
.procname = "seg6_flowlabel",
.data = &init_net.ipv6.sysctl.seg6_flowlabel,
--
2.31.1