include/net/inet_hashtables.h

Source file repositories/reference/linux-study-clean/include/net/inet_hashtables.h

File Facts

System
Linux kernel
Corpus path
include/net/inet_hashtables.h
Extension
.h
Size
16767 bytes
Lines
536
Domain
Networking Core
Bucket
Sockets, Protocols, Packet Path, And Network Policy
Inferred role
Networking Core: implementation source
Status
source implementation candidate

Why This File Exists

Networking stack implementation surface: socket APIs, protocol dispatch, packet flow, routing, filtering, and network namespaces.

Dependency Surface

Detected Declarations

Annotated Snippet

struct inet_ehash_bucket {
	struct hlist_nulls_head chain;
};

/* There are a few simple rules, which allow for local port reuse by
 * an application.  In essence:
 *
 *	1) Sockets bound to different interfaces may share a local port.
 *	   Failing that, goto test 2.
 *	2) If all sockets have sk->sk_reuse set, and none of them are in
 *	   TCP_LISTEN state, the port may be shared.
 *	   Failing that, goto test 3.
 *	3) If all sockets are bound to a specific inet_sk(sk)->rcv_saddr local
 *	   address, and none of them are the same, the port may be
 *	   shared.
 *	   Failing this, the port cannot be shared.
 *
 * The interesting point, is test #2.  This is what an FTP server does
 * all day.  To optimize this case we use a specific flag bit defined
 * below.  As we add sockets to a bind bucket list, we perform a
 * check of: (newsk->sk_reuse && (newsk->sk_state != TCP_LISTEN))
 * As long as all sockets added to a bind bucket pass this test,
 * the flag bit will be set.
 * The resulting situation is that tcp_v[46]_verify_bind() can just check
 * for this flag bit, if it is set and the socket trying to bind has
 * sk->sk_reuse set, we don't even have to walk the owners list at all,
 * we return that it is ok to bind this socket to the requested local port.
 *
 * Sounds like a lot of work, but it is worth it.  In a more naive
 * implementation (ie. current FreeBSD etc.) the entire list of ports
 * must be walked for each data port opened by an ftp server.  Needless
 * to say, this does not scale at all.  With a couple thousand FTP
 * users logged onto your box, isn't it nice to know that new data
 * ports are created in O(1) time?  I thought so. ;-)	-DaveM
 */
#define FASTREUSEPORT_ANY	1
#define FASTREUSEPORT_STRICT	2

struct inet_bind_bucket {
	possible_net_t		ib_net;
	int			l3mdev;
	unsigned short		port;
	signed char		fastreuse;
	signed char		fastreuseport;
	kuid_t			fastuid;
#if IS_ENABLED(CONFIG_IPV6)
	struct in6_addr		fast_v6_rcv_saddr;
#endif
	__be32			fast_rcv_saddr;
	unsigned short		fast_sk_family;
	bool			fast_ipv6_only;
	struct hlist_node	node;
	struct hlist_head	bhash2;
	struct rcu_head		rcu;
};

struct inet_bind2_bucket {
	possible_net_t		ib_net;
	int			l3mdev;
	unsigned short		port;
#if IS_ENABLED(CONFIG_IPV6)
	unsigned short		addr_type;
	struct in6_addr		v6_rcv_saddr;
#define rcv_saddr		v6_rcv_saddr.s6_addr32[3]
#else
	__be32			rcv_saddr;
#endif
	/* Node in the bhash2 inet_bind_hashbucket chain */
	struct hlist_node	node;
	struct hlist_node	bhash_node;
	/* List of sockets hashed to this bucket */
	struct hlist_head	owners;
	signed char		fastreuse;
	signed char		fastreuseport;
};

static inline struct net *ib_net(const struct inet_bind_bucket *ib)
{
	return read_pnet(&ib->ib_net);
}

static inline struct net *ib2_net(const struct inet_bind2_bucket *ib)
{
	return read_pnet(&ib->ib_net);
}

#define inet_bind_bucket_for_each(tb, head) \
	hlist_for_each_entry(tb, head, node)

struct inet_bind_hashbucket {

Annotation

Implementation Notes