sock

/**  * struct sock_common - minimal network layer representation of sockets  * @skc_daddr: Foreign IPv4 addr  * @skc_rcv_saddr: Bound local IPv4 addr  * @skc_hash: hash value used with various protocol lookup tables  * @skc_u16hashes: two u16 hash values used by UDP lookup tables  * @skc_dport: placeholder for inet_dport/tw_dport  * @skc_num: placeholder for inet_num/tw_num  * @skc_family: network address family  * @skc_state: Connection state  * @skc_reuse: %SO_REUSEADDR setting  * @skc_reuseport: %SO_REUSEPORT setting  * @skc_bound_dev_if: bound device index if != 0  * @skc_bind_node: bind hash linkage for various protocol lookup tables  * @skc_portaddr_node: second hash linkage for UDP/UDP-Lite protocol  * @skc_prot: protocol handlers inside a network family  * @skc_net: reference to the network namespace of this socket  * @skc_node: main hash linkage for various protocol lookup tables  * @skc_nulls_node: main hash linkage for TCP/UDP/UDP-Lite protocol  * @skc_tx_queue_mapping: tx queue number for this connection  * @skc_flags: place holder for sk_flags  * %SO_LINGER (l_onoff), %SO_BROADCAST, %SO_KEEPALIVE,  * %SO_OOBINLINE settings, %SO_TIMESTAMPING settings  * @skc_incoming_cpu: record/match cpu processing incoming packets  * @skc_refcnt: reference count  *  * This is the minimal network layer representation of sockets, the header  * for struct sock and struct inet_timewait_sock.  */ struct sock_common { /* skc_daddr and skc_rcv_saddr must be grouped on a 8 bytes aligned * address on 64bit arches : cf INET_MATCH() */ union { __addrpair skc_addrpair; struct { __be32 skc_daddr; __be32 skc_rcv_saddr; }; }; union  { unsigned int skc_hash; __u16 skc_u16hashes[2]; }; /* skc_dport && skc_num must be grouped as well */ union { __portpair skc_portpair; struct { __be16 skc_dport; __u16 skc_num; }; }; unsigned short skc_family; volatile unsigned char skc_state; unsigned char skc_reuse:4; unsigned char skc_reuseport:1; unsigned char skc_ipv6only:1; unsigned char skc_net_refcnt:1; int skc_bound_dev_if; union { struct hlist_node skc_bind_node; struct hlist_node skc_portaddr_node; }; struct proto *skc_prot; possible_net_t skc_net; #if IS_ENABLED(CONFIG_IPV6) struct in6_addr skc_v6_daddr; struct in6_addr skc_v6_rcv_saddr; #endif atomic64_t skc_cookie; /* following fields are padding to force * offset(struct sock, sk_refcnt) == 128 on 64bit arches * assuming IPV6 is enabled. We use this padding differently * for different kind of 'sockets' */ union { unsigned long skc_flags; struct sock *skc_listener; /* request_sock */ struct inet_timewait_death_row *skc_tw_dr; /* inet_timewait_sock */ }; /* * fields between dontcopy_begin/dontcopy_end * are not copied in sock_copy() */ /* private: */ int skc_dontcopy_begin[0]; /* public: */ union { struct hlist_node skc_node; struct hlist_nulls_node skc_nulls_node; }; int skc_tx_queue_mapping; union { int skc_incoming_cpu; u32 skc_rcv_wnd; u32 skc_tw_rcv_nxt; /* struct tcp_timewait_sock  */ }; atomic_t skc_refcnt; /* private: */ int                     skc_dontcopy_end[0]; union { u32 skc_rxhash; u32 skc_window_clamp; u32 skc_tw_snd_nxt; /* struct tcp_timewait_sock */ }; /* public: */ };