linux协议栈RDS代码流程

AF_RDS, PF_RDS, SOL_RDS
	AF_RDS and PF_RDS are the domain type to be used with socket(2)
	to create RDS sockets. SOL_RDS is the socket-level to be used
	with setsockopt(2) and getsockopt(2) for RDS specific socket
	options.

  fd = socket(PF_RDS, SOCK_SEQPACKET, 0);
        This creates a new, unbound RDS socket.

rds发送流程

rds_sendmsg

	rds_send_xmit

		conn->c_trans->xmit	->	rds_tcp_xmit

			rds_tcp_sendmsg

				kernel_sendmsg

					sock_sendmsg -> sock_sendmsg -> sock->ops->sendmsg
					
						tcp_sendmsg

rds收包流程


recvmsg

	rds_recvmsg
	
		rds_next_incoming
        
        	list_entry(rs->rs_recv_queue.next, struct rds_incoming, i_item);

	
===================queue==================

rds_recv_worker

	cp->cp_conn->c_trans->recv_path(cp)

		rds_tcp_recv_path

			rds_tcp_read_sock

				tcp_read_sock

					rds_tcp_data_recv
					
						rds_recv_incoming

							list_add_tail(&inc->i_item, &rs->rs_recv_queue);

rds发送时建立tcp连接

rds_sendmsg
	rds_conn_create_outgoing
		__rds_conn_path_init
			rds_connect_worker
				conn->c_trans->conn_path_connect
					c
						sock_create_kern
						sock->ops->connect

rds_tcp模块初始化

rds_tcp_init_net
	rds_tcp_accept_worker
		rds_tcp_accept_one
			rds_conn_create
				__rds_conn_path_init
					rds_connect_worker
						conn->c_trans->conn_path_connect(cp);
							rds_tcp_conn_path_connect

rdst头部格式

struct cmsghdr {
	__kernel_size_t	cmsg_len;	/* data byte count, including hdr */
        int		cmsg_level;	/* originating protocol */
        int		cmsg_type;	/* protocol-specific type */
};

struct rds_header {
	__be64	h_sequence;
	__be64	h_ack;
	__be32	h_len;
	__be16	h_sport;
	__be16	h_dport;
	u8	h_flags;
	u8	h_credit;
	u8	h_padding[4];
	__sum16	h_csum;

	u8	h_exthdr[RDS_HEADER_EXT_SPACE];
};

rds问题

默认要建立8个连接，建立多连接的好处可能是为了利用多核。
最终必须为ip小的发起即便是大的先发起也要断了重连。

/* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the
 * client's ipaddr < server's ipaddr. Otherwise, close the accepted
 * socket and force a reconneect from smaller -> larger ip addr. The reason
 * we special case cp_index 0 is to allow the rds probe ping itself to itself
 * get through efficiently.
 * Since reconnects are only initiated from the node with the numerically
 * smaller ip address, we recycle conns in RDS_CONN_ERROR on the passive side
 * by moving them to CONNECTING in this function.
 */
static
struct rds_tcp_connection *rds_tcp_accept_one_path(struct rds_connection *conn)
{
	/* for mprds, all paths MUST be initiated by the peer
	 * with the smaller address.
	 */
	if (rds_addr_cmp(&conn->c_faddr, &conn->c_laddr) >= 0) {
		/* Make sure we initiate at least one path if this
		 * has not already been done; rds_start_mprds() will
		 * take care of additional paths, if necessary.
		 */
		if (npaths == 1)
			rds_conn_path_connect_if_down(&conn->c_path[0]);
		return NULL;
	}
}

在网关可以利用rds头部包含最终目的信息。

在服务器可以通过nat进行代理。

//创建netlink操作
static struct rtnl_link_ops link_ops __read_mostly = {
	.kind			= KBUILD_MODNAME,
	.priv_size		= sizeof(struct wg_device),
	.setup			= wg_setup,
	.newlink		= wg_newlink,
};

wg_device_init
    
    wg_device_init
    
    	ret = rtnl_link_register(&link_ops);

//注册wireguard网卡驱动
//注册后通过ip link add dev wg0 type wireguard 创建虚拟网卡
//iplink_modify(RTM_NEWLINK,NLM_F_CREATE|NLM_F_EXCL,argc-1, argv+1);

wg_newlink
    
    register_netdevice
    




#define WG_GENL_NAME "wireguard"

static struct genl_family genl_family __ro_after_init = {
	.ops = genl_ops,
	.n_ops = ARRAY_SIZE(genl_ops),
	.name = WG_GENL_NAME,
	.version = WG_GENL_VERSION,
	.maxattr = WGDEVICE_A_MAX,
	.module = THIS_MODULE,
	.policy = device_policy,
	.netnsok = true
};

wg_genetlink_init(void)

	genl_register_family(&genl_family);