linux/net/mpls/internal.h
Robert Shearman cf4b24f002 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>
2015-10-27 19:52:59 -07:00

134 lines
3.4 KiB
C

#ifndef MPLS_INTERNAL_H
#define MPLS_INTERNAL_H
struct mpls_shim_hdr {
__be32 label_stack_entry;
};
struct mpls_entry_decoded {
u32 label;
u8 ttl;
u8 tc;
u8 bos;
};
struct mpls_dev {
int input_enabled;
struct ctl_table_header *sysctl;
struct rcu_head rcu;
};
struct sk_buff;
#define LABEL_NOT_SPECIFIED (1 << 20)
#define MAX_NEW_LABELS 2
/* This maximum ha length copied from the definition of struct neighbour */
#define VIA_ALEN_ALIGN sizeof(unsigned long)
#define MAX_VIA_ALEN (ALIGN(MAX_ADDR_LEN, VIA_ALEN_ALIGN))
enum mpls_payload_type {
MPT_UNSPEC, /* IPv4 or IPv6 */
MPT_IPV4 = 4,
MPT_IPV6 = 6,
/* Other types not implemented:
* - Pseudo-wire with or without control word (RFC4385)
* - GAL (RFC5586)
*/
};
struct mpls_nh { /* next hop label forwarding entry */
struct net_device __rcu *nh_dev;
u32 nh_label[MAX_NEW_LABELS];
u8 nh_labels;
u8 nh_via_alen;
u8 nh_via_table;
};
/* The route, nexthops and vias are stored together in the same memory
* block:
*
* +----------------------+
* | mpls_route |
* +----------------------+
* | mpls_nh 0 |
* +----------------------+
* | ... |
* +----------------------+
* | mpls_nh n-1 |
* +----------------------+
* | alignment padding |
* +----------------------+
* | via[rt_max_alen] 0 |
* +----------------------+
* | ... |
* +----------------------+
* | via[rt_max_alen] n-1 |
* +----------------------+
*/
struct mpls_route { /* next hop label forwarding entry */
struct rcu_head rt_rcu;
u8 rt_protocol;
u8 rt_payload_type;
u8 rt_max_alen;
unsigned int rt_nhn;
struct mpls_nh rt_nh[0];
};
#define for_nexthops(rt) { \
int nhsel; struct mpls_nh *nh; \
for (nhsel = 0, nh = (rt)->rt_nh; \
nhsel < (rt)->rt_nhn; \
nh++, nhsel++)
#define change_nexthops(rt) { \
int nhsel; struct mpls_nh *nh; \
for (nhsel = 0, nh = (struct mpls_nh *)((rt)->rt_nh); \
nhsel < (rt)->rt_nhn; \
nh++, nhsel++)
#define endfor_nexthops(rt) }
static inline struct mpls_shim_hdr *mpls_hdr(const struct sk_buff *skb)
{
return (struct mpls_shim_hdr *)skb_network_header(skb);
}
static inline struct mpls_shim_hdr mpls_entry_encode(u32 label, unsigned ttl, unsigned tc, bool bos)
{
struct mpls_shim_hdr result;
result.label_stack_entry =
cpu_to_be32((label << MPLS_LS_LABEL_SHIFT) |
(tc << MPLS_LS_TC_SHIFT) |
(bos ? (1 << MPLS_LS_S_SHIFT) : 0) |
(ttl << MPLS_LS_TTL_SHIFT));
return result;
}
static inline struct mpls_entry_decoded mpls_entry_decode(struct mpls_shim_hdr *hdr)
{
struct mpls_entry_decoded result;
unsigned entry = be32_to_cpu(hdr->label_stack_entry);
result.label = (entry & MPLS_LS_LABEL_MASK) >> MPLS_LS_LABEL_SHIFT;
result.ttl = (entry & MPLS_LS_TTL_MASK) >> MPLS_LS_TTL_SHIFT;
result.tc = (entry & MPLS_LS_TC_MASK) >> MPLS_LS_TC_SHIFT;
result.bos = (entry & MPLS_LS_S_MASK) >> MPLS_LS_S_SHIFT;
return result;
}
int nla_put_labels(struct sk_buff *skb, int attrtype, u8 labels,
const u32 label[]);
int nla_get_labels(const struct nlattr *nla, u32 max_labels, u8 *labels,
u32 label[]);
int nla_get_via(const struct nlattr *nla, u8 *via_alen, u8 *via_table,
u8 via[]);
bool mpls_output_possible(const struct net_device *dev);
unsigned int mpls_dev_mtu(const struct net_device *dev);
bool mpls_pkt_too_big(const struct sk_buff *skb, unsigned int mtu);
#endif /* MPLS_INTERNAL_H */