mpls: reduce memory usage of routes
Nexthops for MPLS routes have a via address field sized for the
largest via address that is expected, which is 32 bytes. This means
that in the most common case of having ipv4 via addresses, 28 bytes of
memory more than required are used per nexthop. In the other common
case of an ipv6 nexthop then 16 bytes more than required are
used. With large numbers of MPLS routes this extra memory usage could
start to become significant.
To avoid allocating memory for a maximum length via address when not
all of it is required and to allow for ease of iterating over
nexthops, then the via addresses are changed to be stored in the same
memory block as the route and nexthops, but in an array after the end
of the array of nexthops. New accessors are provided to retrieve a
pointer to the via address.
To allow for O(1) access without having to store a pointer or offset
per nh, the via address for each nexthop is sized according to the
maximum via address for any nexthop in the route, which is stored in a
new route field, rt_max_alen, but this is in an existing hole in
struct mpls_route so it doesn't increase the size of the
structure. Each via address is ensured to be aligned to VIA_ALEN_ALIGN
to account for architectures that don't allow unaligned accesses.
Signed-off-by: Robert Shearman <rshearma@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 1c58662..c70d750 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -57,6 +57,20 @@
}
EXPORT_SYMBOL_GPL(mpls_output_possible);
+static u8 *__mpls_nh_via(struct mpls_route *rt, struct mpls_nh *nh)
+{
+ u8 *nh0_via = PTR_ALIGN((u8 *)&rt->rt_nh[rt->rt_nhn], VIA_ALEN_ALIGN);
+ int nh_index = nh - rt->rt_nh;
+
+ return nh0_via + rt->rt_max_alen * nh_index;
+}
+
+static const u8 *mpls_nh_via(const struct mpls_route *rt,
+ const struct mpls_nh *nh)
+{
+ return __mpls_nh_via((struct mpls_route *)rt, (struct mpls_nh *)nh);
+}
+
static unsigned int mpls_nh_header_size(const struct mpls_nh *nh)
{
/* The size of the layer 2.5 labels to be added for this route */
@@ -303,7 +317,7 @@
}
}
- err = neigh_xmit(nh->nh_via_table, out_dev, nh->nh_via, skb);
+ err = neigh_xmit(nh->nh_via_table, out_dev, mpls_nh_via(rt, nh), skb);
if (err)
net_dbg_ratelimited("%s: packet transmission failed: %d\n",
__func__, err);
@@ -340,14 +354,19 @@
int rc_mp_len;
};
-static struct mpls_route *mpls_rt_alloc(int num_nh)
+static struct mpls_route *mpls_rt_alloc(int num_nh, u8 max_alen)
{
+ u8 max_alen_aligned = ALIGN(max_alen, VIA_ALEN_ALIGN);
struct mpls_route *rt;
- rt = kzalloc(sizeof(*rt) + (num_nh * sizeof(struct mpls_nh)),
+ rt = kzalloc(ALIGN(sizeof(*rt) + num_nh * sizeof(*rt->rt_nh),
+ VIA_ALEN_ALIGN) +
+ num_nh * max_alen_aligned,
GFP_KERNEL);
- if (rt)
+ if (rt) {
rt->rt_nhn = num_nh;
+ rt->rt_max_alen = max_alen_aligned;
+ }
return rt;
}
@@ -408,7 +427,8 @@
}
#if IS_ENABLED(CONFIG_INET)
-static struct net_device *inet_fib_lookup_dev(struct net *net, void *addr)
+static struct net_device *inet_fib_lookup_dev(struct net *net,
+ const void *addr)
{
struct net_device *dev;
struct rtable *rt;
@@ -427,14 +447,16 @@
return dev;
}
#else
-static struct net_device *inet_fib_lookup_dev(struct net *net, void *addr)
+static struct net_device *inet_fib_lookup_dev(struct net *net,
+ const void *addr)
{
return ERR_PTR(-EAFNOSUPPORT);
}
#endif
#if IS_ENABLED(CONFIG_IPV6)
-static struct net_device *inet6_fib_lookup_dev(struct net *net, void *addr)
+static struct net_device *inet6_fib_lookup_dev(struct net *net,
+ const void *addr)
{
struct net_device *dev;
struct dst_entry *dst;
@@ -457,13 +479,15 @@
return dev;
}
#else
-static struct net_device *inet6_fib_lookup_dev(struct net *net, void *addr)
+static struct net_device *inet6_fib_lookup_dev(struct net *net,
+ const void *addr)
{
return ERR_PTR(-EAFNOSUPPORT);
}
#endif
static struct net_device *find_outdev(struct net *net,
+ struct mpls_route *rt,
struct mpls_nh *nh, int oif)
{
struct net_device *dev = NULL;
@@ -471,10 +495,10 @@
if (!oif) {
switch (nh->nh_via_table) {
case NEIGH_ARP_TABLE:
- dev = inet_fib_lookup_dev(net, nh->nh_via);
+ dev = inet_fib_lookup_dev(net, mpls_nh_via(rt, nh));
break;
case NEIGH_ND_TABLE:
- dev = inet6_fib_lookup_dev(net, nh->nh_via);
+ dev = inet6_fib_lookup_dev(net, mpls_nh_via(rt, nh));
break;
case NEIGH_LINK_TABLE:
break;
@@ -492,12 +516,13 @@
return dev;
}
-static int mpls_nh_assign_dev(struct net *net, struct mpls_nh *nh, int oif)
+static int mpls_nh_assign_dev(struct net *net, struct mpls_route *rt,
+ struct mpls_nh *nh, int oif)
{
struct net_device *dev = NULL;
int err = -ENODEV;
- dev = find_outdev(net, nh, oif);
+ dev = find_outdev(net, rt, nh, oif);
if (IS_ERR(dev)) {
err = PTR_ERR(dev);
dev = NULL;
@@ -538,10 +563,10 @@
nh->nh_label[i] = cfg->rc_output_label[i];
nh->nh_via_table = cfg->rc_via_table;
- memcpy(nh->nh_via, cfg->rc_via, cfg->rc_via_alen);
+ memcpy(__mpls_nh_via(rt, nh), cfg->rc_via, cfg->rc_via_alen);
nh->nh_via_alen = cfg->rc_via_alen;
- err = mpls_nh_assign_dev(net, nh, cfg->rc_ifindex);
+ err = mpls_nh_assign_dev(net, rt, nh, cfg->rc_ifindex);
if (err)
goto errout;
@@ -551,8 +576,9 @@
return err;
}
-static int mpls_nh_build(struct net *net, struct mpls_nh *nh,
- int oif, struct nlattr *via, struct nlattr *newdst)
+static int mpls_nh_build(struct net *net, struct mpls_route *rt,
+ struct mpls_nh *nh, int oif,
+ struct nlattr *via, struct nlattr *newdst)
{
int err = -ENOMEM;
@@ -567,11 +593,11 @@
}
err = nla_get_via(via, &nh->nh_via_alen, &nh->nh_via_table,
- nh->nh_via);
+ __mpls_nh_via(rt, nh));
if (err)
goto errout;
- err = mpls_nh_assign_dev(net, nh, oif);
+ err = mpls_nh_assign_dev(net, rt, nh, oif);
if (err)
goto errout;
@@ -581,12 +607,35 @@
return err;
}
-static int mpls_count_nexthops(struct rtnexthop *rtnh, int len)
+static int mpls_count_nexthops(struct rtnexthop *rtnh, int len,
+ u8 cfg_via_alen, u8 *max_via_alen)
{
int nhs = 0;
int remaining = len;
+ if (!rtnh) {
+ *max_via_alen = cfg_via_alen;
+ return 1;
+ }
+
+ *max_via_alen = 0;
+
while (rtnh_ok(rtnh, remaining)) {
+ struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
+ int attrlen;
+
+ attrlen = rtnh_attrlen(rtnh);
+ nla = nla_find(attrs, attrlen, RTA_VIA);
+ if (nla && nla_len(nla) >=
+ offsetof(struct rtvia, rtvia_addr)) {
+ int via_alen = nla_len(nla) -
+ offsetof(struct rtvia, rtvia_addr);
+
+ if (via_alen <= MAX_VIA_ALEN)
+ *max_via_alen = max_t(u16, *max_via_alen,
+ via_alen);
+ }
+
nhs++;
rtnh = rtnh_next(rtnh, &remaining);
}
@@ -631,7 +680,7 @@
if (!nla_via)
goto errout;
- err = mpls_nh_build(cfg->rc_nlinfo.nl_net, nh,
+ err = mpls_nh_build(cfg->rc_nlinfo.nl_net, rt, nh,
rtnh->rtnh_ifindex, nla_via,
nla_newdst);
if (err)
@@ -655,8 +704,9 @@
struct net *net = cfg->rc_nlinfo.nl_net;
struct mpls_route *rt, *old;
int err = -EINVAL;
+ u8 max_via_alen;
unsigned index;
- int nhs = 1; /* default to one nexthop */
+ int nhs;
index = cfg->rc_label;
@@ -693,15 +743,14 @@
if (!(cfg->rc_nlflags & NLM_F_CREATE) && !old)
goto errout;
- if (cfg->rc_mp) {
- err = -EINVAL;
- nhs = mpls_count_nexthops(cfg->rc_mp, cfg->rc_mp_len);
- if (nhs == 0)
- goto errout;
- }
+ err = -EINVAL;
+ nhs = mpls_count_nexthops(cfg->rc_mp, cfg->rc_mp_len,
+ cfg->rc_via_alen, &max_via_alen);
+ if (nhs == 0)
+ goto errout;
err = -ENOMEM;
- rt = mpls_rt_alloc(nhs);
+ rt = mpls_rt_alloc(nhs, max_via_alen);
if (!rt)
goto errout;
@@ -1176,13 +1225,13 @@
if (nla_put_labels(skb, RTA_DST, 1, &label))
goto nla_put_failure;
if (rt->rt_nhn == 1) {
- struct mpls_nh *nh = rt->rt_nh;
+ const struct mpls_nh *nh = rt->rt_nh;
if (nh->nh_labels &&
nla_put_labels(skb, RTA_NEWDST, nh->nh_labels,
nh->nh_label))
goto nla_put_failure;
- if (nla_put_via(skb, nh->nh_via_table, nh->nh_via,
+ if (nla_put_via(skb, nh->nh_via_table, mpls_nh_via(rt, nh),
nh->nh_via_alen))
goto nla_put_failure;
dev = rtnl_dereference(nh->nh_dev);
@@ -1209,7 +1258,7 @@
nh->nh_label))
goto nla_put_failure;
if (nla_put_via(skb, nh->nh_via_table,
- nh->nh_via,
+ mpls_nh_via(rt, nh),
nh->nh_via_alen))
goto nla_put_failure;
@@ -1338,7 +1387,7 @@
/* In case the predefined labels need to be populated */
if (limit > MPLS_LABEL_IPV4NULL) {
struct net_device *lo = net->loopback_dev;
- rt0 = mpls_rt_alloc(1);
+ rt0 = mpls_rt_alloc(1, lo->addr_len);
if (!rt0)
goto nort0;
RCU_INIT_POINTER(rt0->rt_nh->nh_dev, lo);
@@ -1346,11 +1395,12 @@
rt0->rt_payload_type = MPT_IPV4;
rt0->rt_nh->nh_via_table = NEIGH_LINK_TABLE;
rt0->rt_nh->nh_via_alen = lo->addr_len;
- memcpy(rt0->rt_nh->nh_via, lo->dev_addr, lo->addr_len);
+ memcpy(__mpls_nh_via(rt0, rt0->rt_nh), lo->dev_addr,
+ lo->addr_len);
}
if (limit > MPLS_LABEL_IPV6NULL) {
struct net_device *lo = net->loopback_dev;
- rt2 = mpls_rt_alloc(1);
+ rt2 = mpls_rt_alloc(1, lo->addr_len);
if (!rt2)
goto nort2;
RCU_INIT_POINTER(rt2->rt_nh->nh_dev, lo);
@@ -1358,7 +1408,8 @@
rt2->rt_payload_type = MPT_IPV6;
rt2->rt_nh->nh_via_table = NEIGH_LINK_TABLE;
rt2->rt_nh->nh_via_alen = lo->addr_len;
- memcpy(rt2->rt_nh->nh_via, lo->dev_addr, lo->addr_len);
+ memcpy(__mpls_nh_via(rt2, rt2->rt_nh), lo->dev_addr,
+ lo->addr_len);
}
rtnl_lock();
