Code flow chart

sendto recvfrom

+———————————————————————-+ | | | +——–+ +————-+ | | | sendto | Application | recvfrom | | | +—-+—+ +——+——+ | | | | | +————+————————————+——————–+ | | ————-+————————————+———————- | | +————v————————————v——————–+ | Socket Interface | +—–+—+————————————————————+ | +————————————+ ^ ^ | +—————–+————–+ | +—–+———————-+——-+ +——-+—————–+———+ | | | | | | | | | | UDP +——-+—–+ | | | TCP +—–+——-+ | | | | udp_recvmsg | | | | | tcp_recvmsg | | | +-v———–+ +————-+ | |+——v——+ +————-+ | | | udp_sendmsg | +————-+ | || tcp_sendmsg | +————-+ | | +——+——+ | udp_rcv | | |+——+——| | tcp_v4_rcv | | | | +————-+ | | | +————-+ | | | ^ | | | ^ | +———-+——————–+—-+ +——-+—————–+———+ +———-+——————–+————–+—————–+———+ | v | v | | | +————————+ | +—————+ | | | | ip_push_pending_frames | | | ip_queue_xmit | | | | +—-+——————-+ | +—–+———+ | | | | +———————-+————–+ | | | | | +—————-+ +———————–+ | | | v v v | | | | | +———–+ +—–+————-+ +——-+——–+——–+| | | ip_output | | ip_forward_finish | | ip_local_deliver_finish || | +—+——-+ +——————-+ +————————-+| | v ^ ^ | |+——————-+ +—–+——+ +——-+———-+ | || ip_finish_output2 | | ip_forward | | ip_local_deliver | | |+—–+————-+ +————+ +——————+ | | | ^ ^ | | v +——————-+ | | | +———————+ +–+—-+——-+ | | | Neighbor sub system | | ip_rcv_finish | | | +————–+——+ +—————+ | | | ^ | | | +—-+—-+ | | IP | | ip_rcv | | | | +———+ | | | ^ | +—————-+—————————————+—————–+ | | +—————-v—————————————+—————–+ | +—————-+ +—-+—–+ | | | dev_queue_xmit | Driver Interface | netif_rx | | | +——-+——–+ +———-+ | | | ^ | +—————-+—————————————+—————–+ | | +—————-v—————————————+—————–+ | +—————— +—+—-+ | | | net_send_packet | Driver | net_rx | | | +—————–+ +——–+ | +————————————————————————–+

struct sk_buff // include/linux/skbuff.h

+—————————————————————————–+ | | | +———————————————————————–+ | | | +——+ +——+ +——+ +——+ | | +–+->| next |————–>| next |———>| next |———>| next |–+–+ | +——+ +——+ +——+ +——+ | +–| prev |<————–| prev |<———| prev |<———| prev |<-+ +——+ +——+ +——+ +——+ | qlen | | list | | list | | list | +——+ +——+ +——+ +——+ | lock | | sk | | sk | | sk | +——+ +——+ +——+ +——+ | … | | … | | … | +——+ +——+ +——+ | tail | | tail | | tail | +——+ +——+ +——+ | end | | end | | end | +——+ +——+ +——+ | head | | head | | head | +——+ +——+ +——+ | data | | data | | data | +——+ +——+ +——+

struct sk_buff_head struct sk_buff

                        +------+      +----------+
                        | head |      | headroom |
                        +------+      +----------+
                        | data |      |          |
                        +------+      |  data    |
                        | tail |      |          |
                        +------+      +----------+
                        | end  |      | tailroom |
                        +------+      +----------+

struct net_device // include/linux/netdevice.h

        name: eth0

        name_hlist

          state

          next ?

          priv ?

          ....

        netdev_ops

        ethtool_ops

         fwd_ops

          ....

network device create/rigister

alloc_etherdev // include/linux/etherdevice.h alloc_netdev_mqs // net/core/dev.c

e1000_init_module // drivers/net/ethernet/intel/e1000/e1000_main.c | +–> pic_register_driver(&e1000_driver) | +–> e1000_prob | +–> alloc_etherdev

                       +------------------+
                       |   init_module    |
                       +------------------+
                                |
                                v

+——————–+ +——————+ +—————–+ | alloc_etherdev |<—-| do_netcard_probe |——>| rigister_netdev | +———+———-+ +——————+ +—————–+ v +——————–+ | alloc_etherdev_mqs | +———+———-+ v +——————–+ | alloc_netdev_mqs | +———+———-+ v +——————–+ | setup | +——————–+

Reference

struct sk_buff_head # include/linux/skbuff.h

network socket

net/ipv4/af_inet.c static const struct net_proto_family inet_family_ops = { .family = PF_INET, .create = inet_create, .owner = THIS_MODULE, };

/* Upon startup we insert all the elements in inetsw_array[] into

  • the linked list inetsw. */ static struct inet_protosw inetsw_array[] = { { .type = SOCK_STREAM, .protocol = IPPROTO_TCP, .prot = &tcp_prot, .ops = &inet_stream_ops, .flags = INET_PROTOSW_PERMANENT | INET_PROTOSW_ICSK, },

     {
         .type =       SOCK_DGRAM,
         .protocol =   IPPROTO_UDP,
         .prot =       &udp_prot,
         .ops =        &inet_dgram_ops,
         .flags =      INET_PROTOSW_PERMANENT,
},

{
         .type =       SOCK_DGRAM,
         .protocol =   IPPROTO_ICMP,
         .prot =       &ping_prot,
         .ops =        &inet_dgram_ops,
         .flags =      INET_PROTOSW_REUSE,
},

{
        .type =       SOCK_RAW,
        .protocol =   IPPROTO_IP,        /* wild card */
        .prot =       &raw_prot,
        .ops =        &inet_sockraw_ops,
        .flags =      INET_PROTOSW_REUSE,
}

};

const struct proto_ops inet_stream_ops = { .family = PF_INET, .owner = THIS_MODULE, .release = inet_release, .bind = inet_bind, .connect = inet_stream_connect, .socketpair = sock_no_socketpair, .accept = inet_accept, .getname = inet_getname, .poll = tcp_poll, .ioctl = inet_ioctl, .listen = inet_listen, .shutdown = inet_shutdown, .setsockopt = sock_common_setsockopt, .getsockopt = sock_common_getsockopt, .sendmsg = inet_sendmsg, .recvmsg = inet_recvmsg, .mmap = sock_no_mmap, .sendpage = inet_sendpage, .splice_read = tcp_splice_read, #ifdef CONFIG_COMPAT .compat_setsockopt = compat_sock_common_setsockopt, .compat_getsockopt = compat_sock_common_getsockopt, .compat_ioctl = inet_compat_ioctl, #endif }; EXPORT_SYMBOL(inet_stream_ops);

net/ipv4/tcp_ipv4.c struct proto tcp_prot = { .name = “TCP”, .owner = THIS_MODULE, .close = tcp_close, .connect = tcp_v4_connect, .disconnect = tcp_disconnect, .accept = inet_csk_accept, .ioctl = tcp_ioctl, .init = tcp_v4_init_sock, .destroy = tcp_v4_destroy_sock, .shutdown = tcp_shutdown, .setsockopt = tcp_setsockopt, .getsockopt = tcp_getsockopt, .recvmsg = tcp_recvmsg, .sendmsg = tcp_sendmsg, … .h.hashinfo = &tcp_hashinfo, .no_autobind = true, #ifdef CONFIG_COMPAT .compat_setsockopt = compat_tcp_setsockopt, .compat_getsockopt = compat_tcp_getsockopt, #endif #ifdef CONFIG_MEMCG_KMEM .init_cgroup = tcp_init_cgroup, .destroy_cgroup = tcp_destroy_cgroup, .proto_cgroup = tcp_proto_cgroup, #endif }; EXPORT_SYMBOL(tcp_prot);

net/ipv4/af_inet6.c static const struct net_proto_family inet6_family_ops = { .family = PF_INET6, .create = inet6_create, .owner = THIS_MODULE, };

net/ipv6/tcp_ipv6.c

tcpv6_init() -> int6_add_protocol(tcpv6_protocol) -> inet6_register_protosw(tcpv6_protosw)

static const struct inet6_protocol tcpv6_protocol = { .early_demux = tcp_v6_early_demux, .handler = tcp_v6_rcv, .err_handler = tcp_v6_err, .flags = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL, };

static struct inet_protosw tcpv6_protosw = { .type = SOCK_STREAM, .protocol = IPPROTO_TCP, .prot = &tcpv6_prot, .ops = &inet6_stream_ops, .flags = INET_PROTOSW_PERMANENT | INET_PROTOSW_ICSK, };

struct proto tcpv6_prot = { .name = “TCPv6”, .owner = THIS_MODULE, .close = tcp_close, .connect = tcp_v6_connect, .disconnect = tcp_disconnect, .accept = inet_csk_accept, .ioctl = tcp_ioctl, .init = tcp_v6_init_sock, .destroy = tcp_v6_destroy_sock, .shutdown = tcp_shutdown, .setsockopt = tcp_setsockopt, .getsockopt = tcp_getsockopt, .recvmsg = tcp_recvmsg, .sendmsg = tcp_sendmsg, .sendpage = tcp_sendpage, .backlog_rcv = tcp_v6_do_rcv, … .h.hashinfo = &tcp_hashinfo, .no_autobind = true, #ifdef CONFIG_COMPAT .compat_setsockopt = compat_tcp_setsockopt, .compat_getsockopt = compat_tcp_getsockopt, #endif #ifdef CONFIG_MEMCG_KMEM .proto_cgroup = tcp_proto_cgroup, #endif .clear_sk = tcp_v6_clear_sk, };

net/ipv6/af_inet6.c const struct proto_ops inet6_stream_ops = { .family = PF_INET6, .owner = THIS_MODULE, .release = inet6_release, .bind = inet6_bind, .connect = inet_stream_connect, /* ok */ .socketpair = sock_no_socketpair, /* a do nothing */ .accept = inet_accept, /* ok */ .getname = inet6_getname, .poll = tcp_poll, /* ok */ .ioctl = inet6_ioctl, /* must change */ .listen = inet_listen, /* ok */ .shutdown = inet_shutdown, /* ok */ .setsockopt = sock_common_setsockopt, /* ok */ .getsockopt = sock_common_getsockopt, /* ok */ .sendmsg = inet_sendmsg, /* ok */ .recvmsg = inet_recvmsg, /* ok */ .mmap = sock_no_mmap, .sendpage = inet_sendpage, .splice_read = tcp_splice_read, #ifdef CONFIG_COMPAT .compat_setsockopt = compat_sock_common_setsockopt, .compat_getsockopt = compat_sock_common_getsockopt, #endif };