Ability for a user to assign seed value to multipath route hashes.
Now kernel uses random seed value to prevent hash-flooding DoS attacks;
however, it disables some use cases, f.e:
+-------+ +------+ +--------+
| |-eth0---| FW0 |---eth0-| |
| | +------+ | |
| GW0 |ECMP ECMP| GW1 |
| | +------+ | |
| |-eth1---| FW1 |---eth1-| |
+-------+ +------+ +--------+
In this use case, two ECMP routers balance traffic between
two firewalls. If some flow transmits a response over a different channel than
request,
such flow will be dropped, because keep-state rules are created on
the other firewall.
This patch adds sysctl variable: net.ipv4.fib_multipath_hash_seed.
User can set the same seed value on GW0 and GW1 for traffic to be
mirror-balanced. By default, random value is used.
Signed-off-by: Balaev Pavel <balae...@infotecs.ru>
---
Documentation/networking/ip-sysctl.rst | 14 ++++
include/net/flow_dissector.h | 4 +
include/net/netns/ipv4.h | 20 +++++
net/core/flow_dissector.c | 9 +++
net/ipv4/af_inet.c | 5 ++
net/ipv4/route.c | 10 ++-
net/ipv4/sysctl_net_ipv4.c | 104 +++++++++++++++++++++++++
7 files changed, 165 insertions(+), 1 deletion(-)
diff --git a/Documentation/networking/ip-sysctl.rst
b/Documentation/networking/ip-sysctl.rst
index 9701906f6..d1a67e6fe 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -100,6 +100,20 @@ fib_multipath_hash_policy - INTEGER
- 1 - Layer 4
- 2 - Layer 3 or inner Layer 3 if present
+fib_multipath_hash_seed - STRING
+ Controls seed value for multipath route hashes. By default
+ random value is used. Only valid for kernels built with
+ CONFIG_IP_ROUTE_MULTIPATH enabled.
+
+ Valid format: two hex values set off with comma or "random"
+ keyword.
+
+ Example to generate the seed value::
+
+ RAND=$(openssl rand -hex 16) && echo
"${RAND:0:16},${RAND:16:16}"
+
+ Default: "random"
+
fib_sync_mem - UNSIGNED INTEGER
Amount of dirty memory from fib entries that can be backlogged before
synchronize_rcu is forced.
diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index ffd386ea0..2bd4e28de 100644
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -348,6 +348,10 @@ static inline bool flow_keys_have_l4(const struct
flow_keys *keys)
}
u32 flow_hash_from_keys(struct flow_keys *keys);
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+u32 flow_multipath_hash_from_keys(struct flow_keys *keys,
+ const siphash_key_t *seed);
+#endif /* CONFIG_IP_ROUTE_MULTIPATH */
void skb_flow_get_icmp_tci(const struct sk_buff *skb,
struct flow_dissector_key_icmp *key_icmp,
const void *data, int thoff, int hlen);
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 87e161249..70a01817e 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -11,6 +11,14 @@
#include <linux/rcupdate.h>
#include <linux/siphash.h>
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+/* Multipath seed key context */
+struct multipath_seed_ctx {
+ siphash_key_t seed;
+ struct rcu_head rcu;
+};
+#endif
+
struct ctl_table_header;
struct ipv4_devconf;
struct fib_rules_ops;
@@ -222,6 +230,9 @@ struct netns_ipv4 {
#ifdef CONFIG_IP_ROUTE_MULTIPATH
u8 sysctl_fib_multipath_use_neigh;
u8 sysctl_fib_multipath_hash_policy;
+ int sysctl_fib_multipath_hash_seed;
+ struct multipath_seed_ctx __rcu *fib_multipath_hash_seed_ctx;
+ spinlock_t fib_multipath_hash_seed_ctx_lock;
#endif
struct fib_notifier_ops *notifier_ops;
@@ -233,4 +244,13 @@ struct netns_ipv4 {
atomic_t rt_genid;
siphash_key_t ip_id_key;
};
+
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+/* Caller needs to wrap with rcu_read_(un)lock() */
+static inline
+struct multipath_seed_ctx *fib_multipath_seed_get_ctx(const struct netns_ipv4
*ipv4)
+{
+ return rcu_dereference(ipv4->fib_multipath_hash_seed_ctx);
+}
+#endif
#endif
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 5985029e4..457dfdab8 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1560,6 +1560,15 @@ u32 flow_hash_from_keys(struct flow_keys *keys)
}
EXPORT_SYMBOL(flow_hash_from_keys);
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+u32 flow_multipath_hash_from_keys(struct flow_keys *keys,
+ const siphash_key_t *seed)
+{
+ return __flow_hash_from_keys(keys, seed);
+}
+EXPORT_SYMBOL(flow_multipath_hash_from_keys);
+#endif /* CONFIG_IP_ROUTE_MULTIPATH */
+
static inline u32 ___skb_get_hash(const struct sk_buff *skb,
struct flow_keys *keys,
const siphash_key_t *keyval)
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index f17870ee5..fd4c68966 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1874,6 +1874,11 @@ static __net_init int inet_init_net(struct net *net)
net->ipv4.sysctl_fib_notify_on_flag_change = 0;
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+ net->ipv4.fib_multipath_hash_seed_ctx = NULL;
+ spin_lock_init(&net->ipv4.fib_multipath_hash_seed_ctx_lock);
+#endif
+
return 0;
}
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f6787c55f..36f72738d 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1911,6 +1911,7 @@ int fib_multipath_hash(const struct net *net, const
struct flowi4 *fl4,
const struct sk_buff *skb, struct flow_keys *flkeys)
{
u32 multipath_hash = fl4 ? fl4->flowi4_multipath_hash : 0;
+ struct multipath_seed_ctx *seed_ctx;
struct flow_keys hash_keys;
u32 mhash;
@@ -1989,7 +1990,14 @@ int fib_multipath_hash(const struct net *net, const
struct flowi4 *fl4,
}
break;
}
- mhash = flow_hash_from_keys(&hash_keys);
+
+ rcu_read_lock();
+ seed_ctx = fib_multipath_seed_get_ctx(&net->ipv4);
+ if (seed_ctx)
+ mhash = flow_multipath_hash_from_keys(&hash_keys,
&seed_ctx->seed);
+ else
+ mhash = flow_hash_from_keys(&hash_keys);
+ rcu_read_unlock();
if (multipath_hash)
mhash = jhash_2words(mhash, multipath_hash, 0);
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index a09e466ce..38ae8afc0 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -447,6 +447,8 @@ static int proc_tcp_available_ulp(struct ctl_table *ctl,
}
#ifdef CONFIG_IP_ROUTE_MULTIPATH
+#define FIB_MULTIPATH_SEED_KEY_LENGTH sizeof(siphash_key_t)
+#define FIB_MULTIPATH_SEED_RANDOM "random"
static int proc_fib_multipath_hash_policy(struct ctl_table *table, int write,
void *buffer, size_t *lenp,
loff_t *ppos)
@@ -461,6 +463,100 @@ static int proc_fib_multipath_hash_policy(struct
ctl_table *table, int write,
return ret;
}
+
+static void fib_multipath_seed_ctx_free(struct rcu_head *head)
+{
+ struct multipath_seed_ctx *ctx =
+ container_of(head, struct multipath_seed_ctx, rcu);
+
+ kfree_sensitive(ctx);
+}
+
+static int proc_fib_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,
+ ipv4.sysctl_fib_multipath_hash_seed);
+ /* maxlen to print the keys in hex (*2) and a comma in between keys. */
+ struct ctl_table tbl = {
+ .maxlen = ((FIB_MULTIPATH_SEED_KEY_LENGTH * 2) + 2)
+ };
+ siphash_key_t user_key;
+ __le64 key[2];
+ int ret;
+ struct multipath_seed_ctx *ctx;
+
+ tbl.data = kmalloc(tbl.maxlen, GFP_KERNEL);
+
+ if (!tbl.data)
+ return -ENOMEM;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(net->ipv4.fib_multipath_hash_seed_ctx);
+ if (ctx) {
+ put_unaligned_le64(ctx->seed.key[0], &key[0]);
+ put_unaligned_le64(ctx->seed.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", FIB_MULTIPATH_SEED_RANDOM);
+ }
+ rcu_read_unlock();
+
+ ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+
+ if (write && ret == 0) {
+ struct multipath_seed_ctx *new_ctx, *old_ctx;
+
+ if (!strcmp(tbl.data, FIB_MULTIPATH_SEED_RANDOM)) {
+ spin_lock(&net->ipv4.fib_multipath_hash_seed_ctx_lock);
+ old_ctx =
rcu_dereference_protected(net->ipv4.fib_multipath_hash_seed_ctx,
+
lockdep_is_held(&net->ipv4.fib_multipath_hash_seed_ctx_lock));
+ RCU_INIT_POINTER(net->ipv4.fib_multipath_hash_seed_ctx,
NULL);
+
spin_unlock(&net->ipv4.fib_multipath_hash_seed_ctx_lock);
+ if (old_ctx)
+ call_rcu(&old_ctx->rcu,
fib_multipath_seed_ctx_free);
+
+ 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->seed.key[0] = get_unaligned_le64(&key[0]);
+ new_ctx->seed.key[1] = get_unaligned_le64(&key[1]);
+
+ spin_lock(&net->ipv4.fib_multipath_hash_seed_ctx_lock);
+ old_ctx =
rcu_dereference_protected(net->ipv4.fib_multipath_hash_seed_ctx,
+
lockdep_is_held(&net->ipv4.fib_multipath_hash_seed_ctx_lock));
+ rcu_assign_pointer(net->ipv4.fib_multipath_hash_seed_ctx,
new_ctx);
+ spin_unlock(&net->ipv4.fib_multipath_hash_seed_ctx_lock);
+ if (old_ctx)
+ call_rcu(&old_ctx->rcu, fib_multipath_seed_ctx_free);
+ }
+
+out:
+ kfree(tbl.data);
+ return ret;
+}
#endif
static struct ctl_table ipv4_table[] = {
@@ -1052,6 +1148,14 @@ static struct ctl_table ipv4_net_table[] = {
.extra1 = SYSCTL_ZERO,
.extra2 = &two,
},
+ {
+ .procname = "fib_multipath_hash_seed",
+ .data = &init_net.ipv4.sysctl_fib_multipath_hash_seed,
+ /* maxlen to print the keys in hex (*2) and a comma in between
keys. */
+ .maxlen = (FIB_MULTIPATH_SEED_KEY_LENGTH * 2) + 2,
+ .mode = 0600,
+ .proc_handler = proc_fib_multipath_hash_seed,
+ },
#endif
{
.procname = "ip_unprivileged_port_start",
--
2.31.1
