socket.c主要是用来管理各种注册到Linux内核中的网络协议,比如蓝牙,netlink等,我们通过linux文件目录也可以看出来,在\linux-2.6.11\net中,socket.c和各种网络协议文件夹平级。
由于外部用户态程序不关心具体的网络协议,只是利用socket来进行网络通讯,因此socket.c中的代码分布也非常明确,一共分为3部分,
第一部分是系统调用的内核响应实现,一部分是网路协议的注册与管理,一部分是导出到内核态的socket函数,这里简单的笔记下socket.c里面的内容。
PS:
1 代码比较多,而且里面涉及到了文件操作,为了简单起见,这里只简单的笔记下主干操作流程。
2 socket.c是一个代码框架,内部的细节还是由特定的网络协议实现,后续以netlink为例子来具体笔记吧(如果有时间~~)。
/* * NET An implementation of the SOCKET network access protocol. * * Version: @(#)socket.c 1.1.93 18/02/95 * * Authors: Orest Zborowski, <obz@Kodak.COM> * Ross Biro, <bir7@leland.Stanford.Edu> * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> * * Fixes: * Anonymous : NOTSOCK/BADF cleanup. Error fix in * shutdown() * Alan Cox : verify_area() fixes * Alan Cox : Removed DDI * Jonathan Kamens : SOCK_DGRAM reconnect bug * Alan Cox : Moved a load of checks to the very * top level. * Alan Cox : Move address structures to/from user * mode above the protocol layers. * Rob Janssen : Allow 0 length sends. * Alan Cox : Asynchronous I/O support (cribbed from the * tty drivers). * Niibe Yutaka : Asynchronous I/O for writes (4.4BSD style) * Jeff Uphoff : Made max number of sockets command-line * configurable. * Matti Aarnio : Made the number of sockets dynamic, * to be allocated when needed, and mr. * Uphoff's max is used as max to be * allowed to allocate. * Linus : Argh. removed all the socket allocation * altogether: it's in the inode now. * Alan Cox : Made sock_alloc()/sock_release() public * for NetROM and future kernel nfsd type * stuff. * Alan Cox : sendmsg/recvmsg basics. * Tom Dyas : Export net symbols. * Marcin Dalecki : Fixed problems with CONFIG_NET="n". * Alan Cox : Added thread locking to sys_* calls * for sockets. May have errors at the * moment. * Kevin Buhr : Fixed the dumb errors in the above. * Andi Kleen : Some small cleanups, optimizations, * and fixed a copy_from_user() bug. * Tigran Aivazian : sys_send(args) calls sys_sendto(args, NULL, 0) * Tigran Aivazian : Made listen(2) backlog sanity checks * protocol-independent * * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * * This module is effectively the top level interface to the BSD socket * paradigm. * * Based upon Swansea University Computer Society NET3.039 */ #include <linux/config.h> #include <linux/mm.h> #include <linux/smp_lock.h> #include <linux/socket.h> #include <linux/file.h> #include <linux/net.h> #include <linux/interrupt.h> #include <linux/netdevice.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> #include <linux/wanrouter.h> #include <linux/if_bridge.h> #include <linux/init.h> #include <linux/poll.h> #include <linux/cache.h> #include <linux/module.h> #include <linux/highmem.h> #include <linux/divert.h> #include <linux/mount.h> #include <linux/security.h> #include <linux/syscalls.h> #include <linux/compat.h> #include <linux/kmod.h> #ifdef CONFIG_NET_RADIO #include <linux/wireless.h> /* Note : will define WIRELESS_EXT */ #endif /* CONFIG_NET_RADIO */ #include <asm/uaccess.h> #include <asm/unistd.h> #include <net/compat.h> #include <net/sock.h> #include <linux/netfilter.h> static int sock_no_open(struct inode *irrelevant, struct file *dontcare); static ssize_t sock_aio_read(struct kiocb *iocb, char __user *buf, size_t size, loff_t pos); static ssize_t sock_aio_write(struct kiocb *iocb, const char __user *buf, size_t size, loff_t pos); static int sock_mmap(struct file *file, struct vm_area_struct * vma); static int sock_close(struct inode *inode, struct file *file); static unsigned int sock_poll(struct file *file, struct poll_table_struct *wait); static long sock_ioctl(struct file *file, unsigned int cmd, unsigned long arg); static int sock_fasync(int fd, struct file *filp, int on); static ssize_t sock_readv(struct file *file, const struct iovec *vector, unsigned long count, loff_t *ppos); static ssize_t sock_writev(struct file *file, const struct iovec *vector, unsigned long count, loff_t *ppos); static ssize_t sock_sendpage(struct file *file, struct page *page, int offset, size_t size, loff_t *ppos, int more); /* * Socket files have a set of 'special' operations as well as the generic file ones. These don't appear * in the operation structures but are done directly via the socketcall() multiplexor. */ /* socket最终也是绑定到某个文件描述符上,因此也可以认为是文件, 那么就有文件操作。 */ static struct file_operations socket_file_ops = { .owner = THIS_MODULE, .llseek = no_llseek, .aio_read = sock_aio_read, .aio_write = sock_aio_write, .poll = sock_poll, .unlocked_ioctl = sock_ioctl, .mmap = sock_mmap, .open = sock_no_open, /* special open code to disallow open via /proc */ .release = sock_close, .fasync = sock_fasync, .readv = sock_readv, .writev = sock_writev, .sendpage = sock_sendpage }; /* * The protocol list. Each protocol is registered in here. */ static struct net_proto_family *net_families[NPROTO]; #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT) static atomic_t net_family_lockct = ATOMIC_INIT(0); static DEFINE_SPINLOCK(net_family_lock); /* The strategy is: modifications net_family vector are short, do not sleep and veeery rare, but read access should be free of any exclusive locks. */ static void net_family_write_lock(void) { spin_lock(&net_family_lock); while (atomic_read(&net_family_lockct) != 0) { spin_unlock(&net_family_lock); yield(); spin_lock(&net_family_lock); } } static __inline__ void net_family_write_unlock(void) { spin_unlock(&net_family_lock); } static __inline__ void net_family_read_lock(void) { atomic_inc(&net_family_lockct); spin_unlock_wait(&net_family_lock); } static __inline__ void net_family_read_unlock(void) { atomic_dec(&net_family_lockct); } #else #define net_family_write_lock() do { } while(0) #define net_family_write_unlock() do { } while(0) #define net_family_read_lock() do { } while(0) #define net_family_read_unlock() do { } while(0) #endif /* * Statistics counters of the socket lists */ static DEFINE_PER_CPU(int, sockets_in_use) = 0; /* * Support routines. Move socket addresses back and forth across the kernel/user * divide and look after the messy bits. */ #define MAX_SOCK_ADDR 128 /* 108 for Unix domain - 16 for IP, 16 for IPX, 24 for IPv6, about 80 for AX.25 must be at least one bigger than the AF_UNIX size (see net/unix/af_unix.c :unix_mkname()). */ /** * move_addr_to_kernel - copy a socket address into kernel space * @uaddr: Address in user space * @kaddr: Address in kernel space * @ulen: Length in user space * * The address is copied into kernel space. If the provided address is * too long an error code of -EINVAL is returned. If the copy gives * invalid addresses -EFAULT is returned. On a success 0 is returned. */ /* 将用户态addr拷贝到本地kernel */ int move_addr_to_kernel(void __user *uaddr, int ulen, void *kaddr) { if(ulen<0||ulen>MAX_SOCK_ADDR) return -EINVAL; if(ulen==0) return 0; if(copy_from_user(kaddr,uaddr,ulen)) return -EFAULT; return 0; } /** * move_addr_to_user - copy an address to user space * @kaddr: kernel space address * @klen: length of address in kernel * @uaddr: user space address * @ulen: pointer to user length field * * The value pointed to by ulen on entry is the buffer length available. * This is overwritten with the buffer space used. -EINVAL is returned * if an overlong buffer is specified or a negative buffer size. -EFAULT * is returned if either the buffer or the length field are not * accessible. * After copying the data up to the limit the user specifies, the true * length of the data is written over the length limit the user * specified. Zero is returned for a success. */ /* 将本地kernel 中的addr拷贝到用户态 */ int move_addr_to_user(void *kaddr, int klen, void __user *uaddr, int __user *ulen) { int err; int len; if((err=get_user(len, ulen))) return err; if(len>klen) len=klen; if(len<0 || len> MAX_SOCK_ADDR) return -EINVAL; if(len) { if(copy_to_user(uaddr,kaddr,len)) return -EFAULT; } /* * "fromlen shall refer to the value before truncation.." * 1003.1g */ return __put_user(klen, ulen); } #define SOCKFS_MAGIC 0x534F434B static kmem_cache_t * sock_inode_cachep; static struct inode *sock_alloc_inode(struct super_block *sb) { struct socket_alloc *ei; ei = (struct socket_alloc *)kmem_cache_alloc(sock_inode_cachep, SLAB_KERNEL); if (!ei) return NULL; init_waitqueue_head(&ei->socket.wait); ei->socket.fasync_list = NULL; ei->socket.state = SS_UNCONNECTED; ei->socket.flags = 0; ei->socket.ops = NULL; ei->socket.sk = NULL; ei->socket.file = NULL; ei->socket.passcred = 0; return &ei->vfs_inode; } static void sock_destroy_inode(struct inode *inode) { kmem_cache_free(sock_inode_cachep, container_of(inode, struct socket_alloc, vfs_inode)); } static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags) { struct socket_alloc *ei = (struct socket_alloc *) foo; if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) == SLAB_CTOR_CONSTRUCTOR) inode_init_once(&ei->vfs_inode); } static int init_inodecache(void) { sock_inode_cachep = kmem_cache_create("sock_inode_cache", sizeof(struct socket_alloc), 0, SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once, NULL); if (sock_inode_cachep == NULL) return -ENOMEM; return 0; } static struct super_operations sockfs_ops = { .alloc_inode = sock_alloc_inode, .destroy_inode =sock_destroy_inode, .statfs = simple_statfs, }; static struct super_block *sockfs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { return get_sb_pseudo(fs_type, "socket:", &sockfs_ops, SOCKFS_MAGIC); } static struct vfsmount *sock_mnt; static struct file_system_type sock_fs_type = { .name = "sockfs", .get_sb = sockfs_get_sb, .kill_sb = kill_anon_super, }; static int sockfs_delete_dentry(struct dentry *dentry) { return 1; } static struct dentry_operations sockfs_dentry_operations = { .d_delete = sockfs_delete_dentry, }; /* * Obtains the first available file descriptor and sets it up for use. * * This function creates file structure and maps it to fd space * of current process. On success it returns file descriptor * and file struct implicitly stored in sock->file. * Note that another thread may close file descriptor before we return * from this function. We use the fact that now we do not refer * to socket after mapping. If one day we will need it, this * function will increment ref. count on file by 1. * * In any case returned fd MAY BE not valid! * This race condition is unavoidable * with shared fd spaces, we cannot solve it inside kernel, * but we take care of internal coherence yet. */ /* 将socket指针绑定到当前进程上的一个描述符上,并返回描述符 */ int sock_map_fd(struct socket *sock) { int fd; struct qstr this; char name[32]; /* * Find a file descriptor suitable for return to the user. */ fd = get_unused_fd(); if (fd >= 0) { struct file *file = get_empty_filp(); if (!file) { put_unused_fd(fd); fd = -ENFILE; goto out; } /* 根据socket指针来找到socket_alloc中对应的inode指针 */ sprintf(name, "[%lu]", SOCK_INODE(sock)->i_ino); this.name = name; this.len = strlen(name); this.hash = SOCK_INODE(sock)->i_ino; /* 一大堆操作,就是讲socket指针绑到指定的描述符上 */ file->f_dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this); if (!file->f_dentry) { put_filp(file); put_unused_fd(fd); fd = -ENOMEM; goto out; } file->f_dentry->d_op = &sockfs_dentry_operations; d_add(file->f_dentry, SOCK_INODE(sock)); file->f_vfsmnt = mntget(sock_mnt); file->f_mapping = file->f_dentry->d_inode->i_mapping; /* 文件操作,作者猜测如果能够定位到这个文件,应该也可以直接读写进行socket通讯 */ sock->file = file; file->f_op = SOCK_INODE(sock)->i_fop = &socket_file_ops; file->f_mode = FMODE_READ | FMODE_WRITE; file->f_flags = O_RDWR; file->f_pos = 0; fd_install(fd, file); } out: return fd; } /** * sockfd_lookup - Go from a file number to its socket slot * @fd: file handle * @err: pointer to an error code return * * The file handle passed in is locked and the socket it is bound * too is returned. If an error occurs the err pointer is overwritten * with a negative errno code and NULL is returned. The function checks * for both invalid handles and passing a handle which is not a socket. * * On a success the socket object pointer is returned. */ /* 根据文件描述符查询对应的socket指针 */ struct socket *sockfd_lookup(int fd, int *err) { struct file *file; struct inode *inode; struct socket *sock; if (!(file = fget(fd))) { *err = -EBADF; return NULL; } /* 先查inode */ inode = file->f_dentry->d_inode; /* 根据inode在socket_alloc 中查找绑定的socket指针 */ if (!inode->i_sock || !(sock = SOCKET_I(inode))) { *err = -ENOTSOCK; fput(file); return NULL; } if (sock->file != file) { printk(KERN_ERR "socki_lookup: socket file changed!\n"); sock->file = file; } return sock; } /** * sock_alloc - allocate a socket * * Allocate a new inode and socket object. The two are bound together * and initialised. The socket is then returned. If we are out of inodes * NULL is returned. */ /* 生成一个socket_alloc结构体,然后返回里面的socket指针 */ static struct socket *sock_alloc(void) { struct inode * inode; struct socket * sock; inode = new_inode(sock_mnt->mnt_sb); if (!inode) return NULL; sock = SOCKET_I(inode); inode->i_mode = S_IFSOCK|S_IRWXUGO; inode->i_sock = 1; inode->i_uid = current->fsuid; inode->i_gid = current->fsgid; get_cpu_var(sockets_in_use)++; put_cpu_var(sockets_in_use); return sock; } /* * In theory you can't get an open on this inode, but /proc provides * a back door. Remember to keep it shut otherwise you'll let the * creepy crawlies in. */ static int sock_no_open(struct inode *irrelevant, struct file *dontcare) { return -ENXIO; } struct file_operations bad_sock_fops = { .owner = THIS_MODULE, .open = sock_no_open, }; /** * sock_release - close a socket * @sock: socket to close * * The socket is released from the protocol stack if it has a release * callback, and the inode is then released if the socket is bound to * an inode not a file. */ void sock_release(struct socket *sock) { if (sock->ops) { struct module *owner = sock->ops->owner; sock->ops->release(sock); sock->ops = NULL; module_put(owner); } if (sock->fasync_list) printk(KERN_ERR "sock_release: fasync list not empty!\n"); get_cpu_var(sockets_in_use)--; put_cpu_var(sockets_in_use); if (!sock->file) { iput(SOCK_INODE(sock)); return; } sock->file=NULL; } static inline int __sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, size_t size) { struct sock_iocb *si = kiocb_to_siocb(iocb); int err; si->sock = sock; si->scm = NULL; si->msg = msg; si->size = size; err = security_socket_sendmsg(sock, msg, size); if (err) return err; /* 一级级调用,最后调用socket指针里面的协议回调函数 */ return sock->ops->sendmsg(iocb, sock, msg, size); } int sock_sendmsg(struct socket *sock, struct msghdr *msg, size_t size) { struct kiocb iocb; struct sock_iocb siocb; int ret; init_sync_kiocb(&iocb, NULL); iocb.private = &siocb; ret = __sock_sendmsg(&iocb, sock, msg, size); if (-EIOCBQUEUED == ret) ret = wait_on_sync_kiocb(&iocb); return ret; } int kernel_sendmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec, size_t num, size_t size) { mm_segment_t oldfs = get_fs(); int result; set_fs(KERNEL_DS); /* * the following is safe, since for compiler definitions of kvec and * iovec are identical, yielding the same in-core layout and alignment */ msg->msg_iov = (struct iovec *)vec, msg->msg_iovlen = num; result = sock_sendmsg(sock, msg, size); set_fs(oldfs); return result; } static inline int __sock_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, size_t size, int flags) { int err; struct sock_iocb *si = kiocb_to_siocb(iocb); si->sock = sock; si->scm = NULL; si->msg = msg; si->size = size; si->flags = flags; err = security_socket_recvmsg(sock, msg, size, flags); if (err) return err; /* 一级级调用,最后调用socket指针里面的协议回调函数 */ return sock->ops->recvmsg(iocb, sock, msg, size, flags); } int sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, int flags) { struct kiocb iocb; struct sock_iocb siocb; int ret; init_sync_kiocb(&iocb, NULL); iocb.private = &siocb; ret = __sock_recvmsg(&iocb, sock, msg, size, flags); if (-EIOCBQUEUED == ret) ret = wait_on_sync_kiocb(&iocb); return ret; } int kernel_recvmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec, size_t num, size_t size, int flags) { mm_segment_t oldfs = get_fs(); int result; set_fs(KERNEL_DS); /* * the following is safe, since for compiler definitions of kvec and * iovec are identical, yielding the same in-core layout and alignment */ msg->msg_iov = (struct iovec *)vec, msg->msg_iovlen = num; result = sock_recvmsg(sock, msg, size, flags); set_fs(oldfs); return result; } static void sock_aio_dtor(struct kiocb *iocb) { kfree(iocb->private); } /* * Read data from a socket. ubuf is a user mode pointer. We make sure the user * area ubuf...ubuf+size-1 is writable before asking the protocol. */ static ssize_t sock_aio_read(struct kiocb *iocb, char __user *ubuf, size_t size, loff_t pos) { struct sock_iocb *x, siocb; struct socket *sock; int flags; if (pos != 0) return -ESPIPE; if (size==0) /* Match SYS5 behaviour */ return 0; if (is_sync_kiocb(iocb)) x = &siocb; else { x = kmalloc(sizeof(struct sock_iocb), GFP_KERNEL); if (!x) return -ENOMEM; iocb->ki_dtor = sock_aio_dtor; } iocb->private = x; x->kiocb = iocb; sock = SOCKET_I(iocb->ki_filp->f_dentry->d_inode); x->async_msg.msg_name = NULL; x->async_msg.msg_namelen = 0; x->async_msg.msg_iov = &x->async_iov; x->async_msg.msg_iovlen = 1; x->async_msg.msg_control = NULL; x->async_msg.msg_controllen = 0; x->async_iov.iov_base = ubuf; x->async_iov.iov_len = size; flags = !(iocb->ki_filp->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT; return __sock_recvmsg(iocb, sock, &x->async_msg, size, flags); } /* * Write data to a socket. We verify that the user area ubuf..ubuf+size-1 * is readable by the user process. */ static ssize_t sock_aio_write(struct kiocb *iocb, const char __user *ubuf, size_t size, loff_t pos) { struct sock_iocb *x, siocb; struct socket *sock; if (pos != 0) return -ESPIPE; if(size==0) /* Match SYS5 behaviour */ return 0; if (is_sync_kiocb(iocb)) x = &siocb; else { x = kmalloc(sizeof(struct sock_iocb), GFP_KERNEL); if (!x) return -ENOMEM; iocb->ki_dtor = sock_aio_dtor; } iocb->private = x; x->kiocb = iocb; sock = SOCKET_I(iocb->ki_filp->f_dentry->d_inode); x->async_msg.msg_name = NULL; x->async_msg.msg_namelen = 0; x->async_msg.msg_iov = &x->async_iov; x->async_msg.msg_iovlen = 1; x->async_msg.msg_control = NULL; x->async_msg.msg_controllen = 0; x->async_msg.msg_flags = !(iocb->ki_filp->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT; if (sock->type == SOCK_SEQPACKET) x->async_msg.msg_flags |= MSG_EOR; x->async_iov.iov_base = (void __user *)ubuf; x->async_iov.iov_len = size; return __sock_sendmsg(iocb, sock, &x->async_msg, size); } ssize_t sock_sendpage(struct file *file, struct page *page, int offset, size_t size, loff_t *ppos, int more) { struct socket *sock; int flags; sock = SOCKET_I(file->f_dentry->d_inode); flags = !(file->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT; if (more) flags |= MSG_MORE; return sock->ops->sendpage(sock, page, offset, size, flags); } static int sock_readv_writev(int type, struct inode * inode, struct file * file, const struct iovec * iov, long count, size_t size) { struct msghdr msg; struct socket *sock; sock = SOCKET_I(inode); msg.msg_name = NULL; msg.msg_namelen = 0; msg.msg_control = NULL; msg.msg_controllen = 0; msg.msg_iov = (struct iovec *) iov; msg.msg_iovlen = count; msg.msg_flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0; /* read() does a VERIFY_WRITE */ if (type == VERIFY_WRITE) return sock_recvmsg(sock, &msg, size, msg.msg_flags); if (sock->type == SOCK_SEQPACKET) msg.msg_flags |= MSG_EOR; return sock_sendmsg(sock, &msg, size); } static ssize_t sock_readv(struct file *file, const struct iovec *vector, unsigned long count, loff_t *ppos) { size_t tot_len = 0; int i; for (i = 0 ; i < count ; i++) tot_len += vector[i].iov_len; return sock_readv_writev(VERIFY_WRITE, file->f_dentry->d_inode, file, vector, count, tot_len); } static ssize_t sock_writev(struct file *file, const struct iovec *vector, unsigned long count, loff_t *ppos) { size_t tot_len = 0; int i; for (i = 0 ; i < count ; i++) tot_len += vector[i].iov_len; return sock_readv_writev(VERIFY_READ, file->f_dentry->d_inode, file, vector, count, tot_len); } /* * Atomic setting of ioctl hooks to avoid race * with module unload. */ static DECLARE_MUTEX(br_ioctl_mutex); static int (*br_ioctl_hook)(unsigned int cmd, void __user *arg) = NULL; void brioctl_set(int (*hook)(unsigned int, void __user *)) { down(&br_ioctl_mutex); br_ioctl_hook = hook; up(&br_ioctl_mutex); } EXPORT_SYMBOL(brioctl_set); static DECLARE_MUTEX(vlan_ioctl_mutex); static int (*vlan_ioctl_hook)(void __user *arg); void vlan_ioctl_set(int (*hook)(void __user *)) { down(&vlan_ioctl_mutex); vlan_ioctl_hook = hook; up(&vlan_ioctl_mutex); } EXPORT_SYMBOL(vlan_ioctl_set); static DECLARE_MUTEX(dlci_ioctl_mutex); static int (*dlci_ioctl_hook)(unsigned int, void __user *); void dlci_ioctl_set(int (*hook)(unsigned int, void __user *)) { down(&dlci_ioctl_mutex); dlci_ioctl_hook = hook; up(&dlci_ioctl_mutex); } EXPORT_SYMBOL(dlci_ioctl_set); /* * With an ioctl, arg may well be a user mode pointer, but we don't know * what to do with it - that's up to the protocol still. */ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg) { struct socket *sock; void __user *argp = (void __user *)arg; int pid, err; sock = SOCKET_I(file->f_dentry->d_inode); if (cmd >= SIOCDEVPRIVATE && cmd <= (SIOCDEVPRIVATE + 15)) { err = dev_ioctl(cmd, argp); } else #ifdef WIRELESS_EXT if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) { err = dev_ioctl(cmd, argp); } else #endif /* WIRELESS_EXT */ switch (cmd) { case FIOSETOWN: case SIOCSPGRP: err = -EFAULT; if (get_user(pid, (int __user *)argp)) break; err = f_setown(sock->file, pid, 1); break; case FIOGETOWN: case SIOCGPGRP: err = put_user(sock->file->f_owner.pid, (int __user *)argp); break; case SIOCGIFBR: case SIOCSIFBR: case SIOCBRADDBR: case SIOCBRDELBR: err = -ENOPKG; if (!br_ioctl_hook) request_module("bridge"); down(&br_ioctl_mutex); if (br_ioctl_hook) err = br_ioctl_hook(cmd, argp); up(&br_ioctl_mutex); break; case SIOCGIFVLAN: case SIOCSIFVLAN: err = -ENOPKG; if (!vlan_ioctl_hook) request_module("8021q"); down(&vlan_ioctl_mutex); if (vlan_ioctl_hook) err = vlan_ioctl_hook(argp); up(&vlan_ioctl_mutex); break; case SIOCGIFDIVERT: case SIOCSIFDIVERT: /* Convert this to call through a hook */ err = divert_ioctl(cmd, argp); break; case SIOCADDDLCI: case SIOCDELDLCI: err = -ENOPKG; if (!dlci_ioctl_hook) request_module("dlci"); if (dlci_ioctl_hook) { down(&dlci_ioctl_mutex); err = dlci_ioctl_hook(cmd, argp); up(&dlci_ioctl_mutex); } break; default: err = sock->ops->ioctl(sock, cmd, arg); break; } return err; } int sock_create_lite(int family, int type, int protocol, struct socket **res) { int err; struct socket *sock = NULL; err = security_socket_create(family, type, protocol, 1); if (err) goto out; sock = sock_alloc(); if (!sock) { err = -ENOMEM; goto out; } security_socket_post_create(sock, family, type, protocol, 1); sock->type = type; out: *res = sock; return err; } /* No kernel lock held - perfect */ static unsigned int sock_poll(struct file *file, poll_table * wait) { struct socket *sock; /* * We can't return errors to poll, so it's either yes or no. */ sock = SOCKET_I(file->f_dentry->d_inode); return sock->ops->poll(file, sock, wait); } static int sock_mmap(struct file * file, struct vm_area_struct * vma) { struct socket *sock = SOCKET_I(file->f_dentry->d_inode); return sock->ops->mmap(file, sock, vma); } int sock_close(struct inode *inode, struct file *filp) { /* * It was possible the inode is NULL we were * closing an unfinished socket. */ if (!inode) { printk(KERN_DEBUG "sock_close: NULL inode\n"); return 0; } sock_fasync(-1, filp, 0); sock_release(SOCKET_I(inode)); return 0; } /* * Update the socket async list * * Fasync_list locking strategy. * * 1. fasync_list is modified only under process context socket lock * i.e. under semaphore. * 2. fasync_list is used under read_lock(&sk->sk_callback_lock) * or under socket lock. * 3. fasync_list can be used from softirq context, so that * modification under socket lock have to be enhanced with * write_lock_bh(&sk->sk_callback_lock). * --ANK (990710) */ static int sock_fasync(int fd, struct file *filp, int on) { struct fasync_struct *fa, *fna=NULL, **prev; struct socket *sock; struct sock *sk; if (on) { fna=(struct fasync_struct *)kmalloc(sizeof(struct fasync_struct), GFP_KERNEL); if(fna==NULL) return -ENOMEM; } sock = SOCKET_I(filp->f_dentry->d_inode); if ((sk=sock->sk) == NULL) { if (fna) kfree(fna); return -EINVAL; } lock_sock(sk); prev=&(sock->fasync_list); for (fa=*prev; fa!=NULL; prev=&fa->fa_next,fa=*prev) if (fa->fa_file==filp) break; if(on) { if(fa!=NULL) { write_lock_bh(&sk->sk_callback_lock); fa->fa_fd=fd; write_unlock_bh(&sk->sk_callback_lock); kfree(fna); goto out; } fna->fa_file=filp; fna->fa_fd=fd; fna->magic=FASYNC_MAGIC; fna->fa_next=sock->fasync_list; write_lock_bh(&sk->sk_callback_lock); sock->fasync_list=fna; write_unlock_bh(&sk->sk_callback_lock); } else { if (fa!=NULL) { write_lock_bh(&sk->sk_callback_lock); *prev=fa->fa_next; write_unlock_bh(&sk->sk_callback_lock); kfree(fa); } } out: release_sock(sock->sk); return 0; } /* This function may be called only under socket lock or callback_lock */ int sock_wake_async(struct socket *sock, int how, int band) { if (!sock || !sock->fasync_list) return -1; switch (how) { case 1: if (test_bit(SOCK_ASYNC_WAITDATA, &sock->flags)) break; goto call_kill; case 2: if (!test_and_clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags)) break; /* fall through */ case 0: call_kill: __kill_fasync(sock->fasync_list, SIGIO, band); break; case 3: __kill_fasync(sock->fasync_list, SIGURG, band); } return 0; } /* 根据用户请求,本地创建一个socket指针,并使用特定的协议来初始化, 这样后续用户就可以根据这socket指针来操作对应的协议 */ static int __sock_create(int family, int type, int protocol, struct socket **res, int kern) { int err; struct socket *sock; /* * Check protocol is in range */ if (family < 0 || family >= NPROTO) return -EAFNOSUPPORT; if (type < 0 || type >= SOCK_MAX) return -EINVAL; /* Compatibility. This uglymoron is moved from INET layer to here to avoid deadlock in module load. */ if (family == PF_INET && type == SOCK_PACKET) { static int warned; if (!warned) { warned = 1; printk(KERN_INFO "%s uses obsolete (PF_INET,SOCK_PACKET)\n", current->comm); } family = PF_PACKET; } err = security_socket_create(family, type, protocol, kern); if (err) return err; #if defined(CONFIG_KMOD) /* Attempt to load a protocol module if the find failed. * * 12/09/1996 Marcin: But! this makes REALLY only sense, if the user * requested real, full-featured networking support upon configuration. * Otherwise module support will break! */ if (net_families[family]==NULL) { request_module("net-pf-%d",family); } #endif net_family_read_lock(); if (net_families[family] == NULL) { err = -EAFNOSUPPORT; goto out; } /* * Allocate the socket and allow the family to set things up. if * the protocol is 0, the family is instructed to select an appropriate * default. */ /* 生成一个socket指针 */ if (!(sock = sock_alloc())) { printk(KERN_WARNING "socket: no more sockets\n"); err = -ENFILE; /* Not exactly a match, but its the closest posix thing */ goto out; } sock->type = type; /* type 赋值 */ /* * We will call the ->create function, that possibly is in a loadable * module, so we have to bump that loadable module refcnt first. */ err = -EAFNOSUPPORT; if (!try_module_get(net_families[family]->owner)) goto out_release; /* 非常重要!! 使用特定的协议来初始化socket指针 */ if ((err = net_families[family]->create(sock, protocol)) < 0) goto out_module_put; /* * Now to bump the refcnt of the [loadable] module that owns this * socket at sock_release time we decrement its refcnt. */ if (!try_module_get(sock->ops->owner)) { sock->ops = NULL; goto out_module_put; } /* * Now that we're done with the ->create function, the [loadable] * module can have its refcnt decremented */ module_put(net_families[family]->owner); *res = sock; security_socket_post_create(sock, family, type, protocol, kern); out: net_family_read_unlock(); return err; out_module_put: module_put(net_families[family]->owner); out_release: sock_release(sock); goto out; } int sock_create(int family, int type, int protocol, struct socket **res) { return __sock_create(family, type, protocol, res, 0); } int sock_create_kern(int family, int type, int protocol, struct socket **res) { return __sock_create(family, type, protocol, res, 1); } asmlinkage long sys_socket(int family, int type, int protocol) { int retval; struct socket *sock; /* 创建一个socket指针并用特定的协议来对其初始化 */ retval = sock_create(family, type, protocol, &sock); if (retval < 0) goto out; /* 根据socket指针绑定一个可用的文件描述符,并返回该描述符 */ retval = sock_map_fd(sock); if (retval < 0) goto out_release; out: /* It may be already another descriptor 8) Not kernel problem. */ return retval; out_release: sock_release(sock); return retval; } /* * Create a pair of connected sockets. */ asmlinkage long sys_socketpair(int family, int type, int protocol, int __user *usockvec) { struct socket *sock1, *sock2; int fd1, fd2, err; /* * Obtain the first socket and check if the underlying protocol * supports the socketpair call. */ err = sock_create(family, type, protocol, &sock1); if (err < 0) goto out; err = sock_create(family, type, protocol, &sock2); if (err < 0) goto out_release_1; err = sock1->ops->socketpair(sock1, sock2); if (err < 0) goto out_release_both; fd1 = fd2 = -1; err = sock_map_fd(sock1); if (err < 0) goto out_release_both; fd1 = err; err = sock_map_fd(sock2); if (err < 0) goto out_close_1; fd2 = err; /* fd1 and fd2 may be already another descriptors. * Not kernel problem. */ err = put_user(fd1, &usockvec[0]); if (!err) err = put_user(fd2, &usockvec[1]); if (!err) return 0; sys_close(fd2); sys_close(fd1); return err; out_close_1: sock_release(sock2); sys_close(fd1); return err; out_release_both: sock_release(sock2); out_release_1: sock_release(sock1); out: return err; } /* * Bind a name to a socket. Nothing much to do here since it's * the protocol's responsibility to handle the local address. * * We move the socket address to kernel space before we call * the protocol layer (having also checked the address is ok). */ /* bind的系统调用的实现 */ asmlinkage long sys_bind(int fd, struct sockaddr __user *umyaddr, int addrlen) { struct socket *sock; char address[MAX_SOCK_ADDR]; int err; /* 根据文件描述符找到对应的socket指针 */ if((sock = sockfd_lookup(fd,&err))!=NULL) { if((err=move_addr_to_kernel(umyaddr,addrlen,address))>=0) { err = security_socket_bind(sock, (struct sockaddr *)address, addrlen); if (err) { sockfd_put(sock); return err; } /* 调用该socket指针的bind函数 */ err = sock->ops->bind(sock, (struct sockaddr *)address, addrlen); } sockfd_put(sock); } return err; } /* * Perform a listen. Basically, we allow the protocol to do anything * necessary for a listen, and if that works, we mark the socket as * ready for listening. */ int sysctl_somaxconn = SOMAXCONN; /* listen 的系统调用的实现 */ asmlinkage long sys_listen(int fd, int backlog) { struct socket *sock; int err; /* 根据文件描述符找到对应的socket指针 */ if ((sock = sockfd_lookup(fd, &err)) != NULL) { if ((unsigned) backlog > sysctl_somaxconn) backlog = sysctl_somaxconn; err = security_socket_listen(sock, backlog); if (err) { sockfd_put(sock); return err; } /* 调用该socket指针的connect函数 */ err=sock->ops->listen(sock, backlog); sockfd_put(sock); } return err; } /* * For accept, we attempt to create a new socket, set up the link * with the client, wake up the client, then return the new * connected fd. We collect the address of the connector in kernel * space and move it to user at the very end. This is unclean because * we open the socket then return an error. * * 1003.1g adds the ability to recvmsg() to query connection pending * status to recvmsg. We need to add that support in a way thats * clean when we restucture accept also. */ asmlinkage long sys_accept(int fd, struct sockaddr __user *upeer_sockaddr, int __user *upeer_addrlen) { struct socket *sock, *newsock; int err, len; char address[MAX_SOCK_ADDR]; sock = sockfd_lookup(fd, &err); if (!sock) goto out; err = -ENFILE; if (!(newsock = sock_alloc())) goto out_put; newsock->type = sock->type; newsock->ops = sock->ops; err = security_socket_accept(sock, newsock); if (err) goto out_release; /* * We don't need try_module_get here, as the listening socket (sock) * has the protocol module (sock->ops->owner) held. */ __module_get(newsock->ops->owner); err = sock->ops->accept(sock, newsock, sock->file->f_flags); if (err < 0) goto out_release; if (upeer_sockaddr) { if(newsock->ops->getname(newsock, (struct sockaddr *)address, &len, 2)<0) { err = -ECONNABORTED; goto out_release; } err = move_addr_to_user(address, len, upeer_sockaddr, upeer_addrlen); if (err < 0) goto out_release; } /* File flags are not inherited via accept() unlike another OSes. */ if ((err = sock_map_fd(newsock)) < 0) goto out_release; security_socket_post_accept(sock, newsock); out_put: sockfd_put(sock); out: return err; out_release: sock_release(newsock); goto out_put; } /* * Attempt to connect to a socket with the server address. The address * is in user space so we verify it is OK and move it to kernel space. * * For 1003.1g we need to add clean support for a bind to AF_UNSPEC to * break bindings * * NOTE: 1003.1g draft 6.3 is broken with respect to AX.25/NetROM and * other SEQPACKET protocols that take time to connect() as it doesn't * include the -EINPROGRESS status for such sockets. */ /* connect 的系统调用的实现 */ asmlinkage long sys_connect(int fd, struct sockaddr __user *uservaddr, int addrlen) { struct socket *sock; char address[MAX_SOCK_ADDR]; int err; /* 根据文件描述符找到对应的socket指针 */ sock = sockfd_lookup(fd, &err); if (!sock) goto out; err = move_addr_to_kernel(uservaddr, addrlen, address); if (err < 0) goto out_put; err = security_socket_connect(sock, (struct sockaddr *)address, addrlen); if (err) goto out_put; /* 调用该socket指针的connect函数 */ err = sock->ops->connect(sock, (struct sockaddr *) address, addrlen, sock->file->f_flags); out_put: sockfd_put(sock); out: return err; } /* * Get the local address ('name') of a socket object. Move the obtained * name to user space. */ asmlinkage long sys_getsockname(int fd, struct sockaddr __user *usockaddr, int __user *usockaddr_len) { struct socket *sock; char address[MAX_SOCK_ADDR]; int len, err; sock = sockfd_lookup(fd, &err); if (!sock) goto out; err = security_socket_getsockname(sock); if (err) goto out_put; err = sock->ops->getname(sock, (struct sockaddr *)address, &len, 0); if (err) goto out_put; err = move_addr_to_user(address, len, usockaddr, usockaddr_len); out_put: sockfd_put(sock); out: return err; } /* * Get the remote address ('name') of a socket object. Move the obtained * name to user space. */ asmlinkage long sys_getpeername(int fd, struct sockaddr __user *usockaddr, int __user *usockaddr_len) { struct socket *sock; char address[MAX_SOCK_ADDR]; int len, err; if ((sock = sockfd_lookup(fd, &err))!=NULL) { err = security_socket_getpeername(sock); if (err) { sockfd_put(sock); return err; } err = sock->ops->getname(sock, (struct sockaddr *)address, &len, 1); if (!err) err=move_addr_to_user(address,len, usockaddr, usockaddr_len); sockfd_put(sock); } return err; } /* * Send a datagram to a given address. We move the address into kernel * space and check the user space data area is readable before invoking * the protocol. */ /* 将一个用户态数据包发送到网络中 */ asmlinkage long sys_sendto(int fd, void __user * buff, size_t len, unsigned flags, struct sockaddr __user *addr, int addr_len) { struct socket *sock; char address[MAX_SOCK_ADDR]; int err; struct msghdr msg; struct iovec iov; /* 首先根据文件描述符获取对应的socket指针 */ sock = sockfd_lookup(fd, &err); if (!sock) goto out; /* buffer一般较大,这里不直接进行用户态向内核态拷贝,而是后面处理(memcpy_fromiovec/iovec.c) 这里先建立一个iovec把信息存下来 */ iov.iov_base=buff; iov.iov_len=len; msg.msg_name=NULL; msg.msg_iov=&iov; msg.msg_iovlen=1; msg.msg_control=NULL; msg.msg_controllen=0; msg.msg_namelen=0; /* 如果用户指定了地址,一般是udp方式。这里统一处理下 */ if(addr) { err = move_addr_to_kernel(addr, addr_len, address); if (err < 0) goto out_put; msg.msg_name=address; msg.msg_namelen=addr_len; } if (sock->file->f_flags & O_NONBLOCK) flags |= MSG_DONTWAIT; msg.msg_flags = flags; err = sock_sendmsg(sock, &msg, len); out_put: sockfd_put(sock); out: return err; } /* * Send a datagram down a socket. */ /* 系统调用,发送buffer到网络中 */ asmlinkage long sys_send(int fd, void __user * buff, size_t len, unsigned flags) { return sys_sendto(fd, buff, len, flags, NULL, 0); } /* * Receive a frame from the socket and optionally record the address of the * sender. We verify the buffers are writable and if needed move the * sender address from kernel to user space. */ /*从网络中获取一个数据包并送到用户态 */ asmlinkage long sys_recvfrom(int fd, void __user * ubuf, size_t size, unsigned flags, struct sockaddr __user *addr, int __user *addr_len) { struct socket *sock; struct iovec iov; struct msghdr msg; char address[MAX_SOCK_ADDR]; int err,err2; /* 首先根据文件描述符获取对应的socket指针 */ sock = sockfd_lookup(fd, &err); if (!sock) goto out; /* buffer一般较大,这里不直接进行拷贝,而是后面处理(memcpy_toiovec/iovec.c) 这里先建立一个iovec把信息存下来 */ msg.msg_control=NULL; msg.msg_controllen=0; msg.msg_iovlen=1; msg.msg_iov=&iov; iov.iov_len=size; iov.iov_base=ubuf; msg.msg_name=address; msg.msg_namelen=MAX_SOCK_ADDR; if (sock->file->f_flags & O_NONBLOCK) flags |= MSG_DONTWAIT; err=sock_recvmsg(sock, &msg, size, flags); if(err >= 0 && addr != NULL) { err2=move_addr_to_user(address, msg.msg_namelen, addr, addr_len); if(err2<0) err=err2; } sockfd_put(sock); out: return err; } /* * Receive a datagram from a socket. */ /*从网络中获取一个数据包并送到用户态 */ asmlinkage long sys_recv(int fd, void __user * ubuf, size_t size, unsigned flags) { return sys_recvfrom(fd, ubuf, size, flags, NULL, NULL); } /* * Set a socket option. Because we don't know the option lengths we have * to pass the user mode parameter for the protocols to sort out. */ asmlinkage long sys_setsockopt(int fd, int level, int optname, char __user *optval, int optlen) { int err; struct socket *sock; if (optlen < 0) return -EINVAL; if ((sock = sockfd_lookup(fd, &err))!=NULL) { err = security_socket_setsockopt(sock,level,optname); if (err) { sockfd_put(sock); return err; } if (level == SOL_SOCKET) err=sock_setsockopt(sock,level,optname,optval,optlen); else err=sock->ops->setsockopt(sock, level, optname, optval, optlen); sockfd_put(sock); } return err; } /* * Get a socket option. Because we don't know the option lengths we have * to pass a user mode parameter for the protocols to sort out. */ asmlinkage long sys_getsockopt(int fd, int level, int optname, char __user *optval, int __user *optlen) { int err; struct socket *sock; if ((sock = sockfd_lookup(fd, &err))!=NULL) { err = security_socket_getsockopt(sock, level, optname); if (err) { sockfd_put(sock); return err; } if (level == SOL_SOCKET) err=sock_getsockopt(sock,level,optname,optval,optlen); else err=sock->ops->getsockopt(sock, level, optname, optval, optlen); sockfd_put(sock); } return err; } /* * Shutdown a socket. */ asmlinkage long sys_shutdown(int fd, int how) { int err; struct socket *sock; if ((sock = sockfd_lookup(fd, &err))!=NULL) { err = security_socket_shutdown(sock, how); if (err) { sockfd_put(sock); return err; } err=sock->ops->shutdown(sock, how); sockfd_put(sock); } return err; } /* A couple of helpful macros for getting the address of the 32/64 bit * fields which are the same type (int / unsigned) on our platforms. */ #define COMPAT_MSG(msg, member) ((MSG_CMSG_COMPAT & flags) ? &msg##_compat->member : &msg->member) #define COMPAT_NAMELEN(msg) COMPAT_MSG(msg, msg_namelen) #define COMPAT_FLAGS(msg) COMPAT_MSG(msg, msg_flags) /* * BSD sendmsg interface */ /* sendmsg系统调用的实现 */ asmlinkage long sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags) { struct compat_msghdr __user *msg_compat = (struct compat_msghdr __user *)msg; struct socket *sock; char address[MAX_SOCK_ADDR]; struct iovec iovstack[UIO_FASTIOV], *iov = iovstack; unsigned char ctl[sizeof(struct cmsghdr) + 20]; /* 20 is size of ipv6_pktinfo */ unsigned char *ctl_buf = ctl; struct msghdr msg_sys; int err, ctl_len, iov_size, total_len; /* 由于sendmsg是直接发送裸数据,因此需要先从用户态数据中搞到消息头并解析 */ err = -EFAULT; if (MSG_CMSG_COMPAT & flags) { if (get_compat_msghdr(&msg_sys, msg_compat)) return -EFAULT; } else if (copy_from_user(&msg_sys, msg, sizeof(struct msghdr))) return -EFAULT; /* 根据文件描述符获取指定socket指针 */ sock = sockfd_lookup(fd, &err); if (!sock) goto out; /* do not move before msg_sys is valid */ err = -EMSGSIZE; if (msg_sys.msg_iovlen > UIO_MAXIOV) goto out_put; /* Check whether to allocate the iovec area*/ err = -ENOMEM; iov_size = msg_sys.msg_iovlen * sizeof(struct iovec); if (msg_sys.msg_iovlen > UIO_FASTIOV) { iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL); if (!iov) goto out_put; } /* This will also move the address data into kernel space */ if (MSG_CMSG_COMPAT & flags) { err = verify_compat_iovec(&msg_sys, iov, address, VERIFY_READ); } else err = verify_iovec(&msg_sys, iov, address, VERIFY_READ); if (err < 0) goto out_freeiov; total_len = err; err = -ENOBUFS; if (msg_sys.msg_controllen > INT_MAX) goto out_freeiov; ctl_len = msg_sys.msg_controllen; if ((MSG_CMSG_COMPAT & flags) && ctl_len) { err = cmsghdr_from_user_compat_to_kern(&msg_sys, ctl, sizeof(ctl)); if (err) goto out_freeiov; ctl_buf = msg_sys.msg_control; } else if (ctl_len) { if (ctl_len > sizeof(ctl)) { ctl_buf = sock_kmalloc(sock->sk, ctl_len, GFP_KERNEL); if (ctl_buf == NULL) goto out_freeiov; } err = -EFAULT; /* * Careful! Before this, msg_sys.msg_control contains a user pointer. * Afterwards, it will be a kernel pointer. Thus the compiler-assisted * checking falls down on this. */ if (copy_from_user(ctl_buf, (void __user *) msg_sys.msg_control, ctl_len)) goto out_freectl; msg_sys.msg_control = ctl_buf; } msg_sys.msg_flags = flags; if (sock->file->f_flags & O_NONBLOCK) msg_sys.msg_flags |= MSG_DONTWAIT; /* 经过各种解析和转换,最终还是构造成标准的msg,然后走标准发送流程 */ err = sock_sendmsg(sock, &msg_sys, total_len); out_freectl: if (ctl_buf != ctl) sock_kfree_s(sock->sk, ctl_buf, ctl_len); out_freeiov: if (iov != iovstack) sock_kfree_s(sock->sk, iov, iov_size); out_put: sockfd_put(sock); out: return err; } /* * BSD recvmsg interface */ /* recvmsg系统调用的实现 */ asmlinkage long sys_recvmsg(int fd, struct msghdr __user *msg, unsigned int flags) { struct compat_msghdr __user *msg_compat = (struct compat_msghdr __user *)msg; struct socket *sock; struct iovec iovstack[UIO_FASTIOV]; struct iovec *iov=iovstack; struct msghdr msg_sys; unsigned long cmsg_ptr; int err, iov_size, total_len, len; /* kernel mode address */ char addr[MAX_SOCK_ADDR]; /* user mode address pointers */ struct sockaddr __user *uaddr; int __user *uaddr_len; if (MSG_CMSG_COMPAT & flags) { if (get_compat_msghdr(&msg_sys, msg_compat)) return -EFAULT; } else if (copy_from_user(&msg_sys,msg,sizeof(struct msghdr))) return -EFAULT; sock = sockfd_lookup(fd, &err); if (!sock) goto out; err = -EMSGSIZE; if (msg_sys.msg_iovlen > UIO_MAXIOV) goto out_put; /* Check whether to allocate the iovec area*/ err = -ENOMEM; iov_size = msg_sys.msg_iovlen * sizeof(struct iovec); if (msg_sys.msg_iovlen > UIO_FASTIOV) { iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL); if (!iov) goto out_put; } /* * Save the user-mode address (verify_iovec will change the * kernel msghdr to use the kernel address space) */ uaddr = (void __user *) msg_sys.msg_name; uaddr_len = COMPAT_NAMELEN(msg); if (MSG_CMSG_COMPAT & flags) { err = verify_compat_iovec(&msg_sys, iov, addr, VERIFY_WRITE); } else err = verify_iovec(&msg_sys, iov, addr, VERIFY_WRITE); if (err < 0) goto out_freeiov; total_len=err; cmsg_ptr = (unsigned long)msg_sys.msg_control; msg_sys.msg_flags = 0; if (MSG_CMSG_COMPAT & flags) msg_sys.msg_flags = MSG_CMSG_COMPAT; if (sock->file->f_flags & O_NONBLOCK) flags |= MSG_DONTWAIT; err = sock_recvmsg(sock, &msg_sys, total_len, flags); if (err < 0) goto out_freeiov; len = err; if (uaddr != NULL) { err = move_addr_to_user(addr, msg_sys.msg_namelen, uaddr, uaddr_len); if (err < 0) goto out_freeiov; } err = __put_user(msg_sys.msg_flags, COMPAT_FLAGS(msg)); if (err) goto out_freeiov; if (MSG_CMSG_COMPAT & flags) err = __put_user((unsigned long)msg_sys.msg_control-cmsg_ptr, &msg_compat->msg_controllen); else err = __put_user((unsigned long)msg_sys.msg_control-cmsg_ptr, &msg->msg_controllen); if (err) goto out_freeiov; err = len; out_freeiov: if (iov != iovstack) sock_kfree_s(sock->sk, iov, iov_size); out_put: sockfd_put(sock); out: return err; } #ifdef __ARCH_WANT_SYS_SOCKETCALL /* Argument list sizes for sys_socketcall */ #define AL(x) ((x) * sizeof(unsigned long)) static unsigned char nargs[18]={AL(0),AL(3),AL(3),AL(3),AL(2),AL(3), AL(3),AL(3),AL(4),AL(4),AL(4),AL(6), AL(6),AL(2),AL(5),AL(5),AL(3),AL(3)}; #undef AL /* * System call vectors. * * Argument checking cleaned up. Saved 20% in size. * This function doesn't need to set the kernel lock because * it is set by the callees. */ /* 系统调用函数入口 */ asmlinkage long sys_socketcall(int call, unsigned long __user *args) { unsigned long a[6]; unsigned long a0,a1; int err; if(call<1||call>SYS_RECVMSG) return -EINVAL; /* 获取用户态输入的数据 */ /* copy_from_user should be SMP safe. */ if (copy_from_user(a, args, nargs[call])) return -EFAULT; a0=a[0]; a1=a[1]; switch(call) { case SYS_SOCKET: err = sys_socket(a0,a1,a[2]); break; case SYS_BIND: err = sys_bind(a0,(struct sockaddr __user *)a1, a[2]); break; case SYS_CONNECT: err = sys_connect(a0, (struct sockaddr __user *)a1, a[2]); break; case SYS_LISTEN: err = sys_listen(a0,a1); break; case SYS_ACCEPT: err = sys_accept(a0,(struct sockaddr __user *)a1, (int __user *)a[2]); break; case SYS_GETSOCKNAME: err = sys_getsockname(a0,(struct sockaddr __user *)a1, (int __user *)a[2]); break; case SYS_GETPEERNAME: err = sys_getpeername(a0, (struct sockaddr __user *)a1, (int __user *)a[2]); break; case SYS_SOCKETPAIR: err = sys_socketpair(a0,a1, a[2], (int __user *)a[3]); break; case SYS_SEND: err = sys_send(a0, (void __user *)a1, a[2], a[3]); break; case SYS_SENDTO: err = sys_sendto(a0,(void __user *)a1, a[2], a[3], (struct sockaddr __user *)a[4], a[5]); break; case SYS_RECV: err = sys_recv(a0, (void __user *)a1, a[2], a[3]); break; case SYS_RECVFROM: err = sys_recvfrom(a0, (void __user *)a1, a[2], a[3], (struct sockaddr __user *)a[4], (int __user *)a[5]); break; case SYS_SHUTDOWN: err = sys_shutdown(a0,a1); break; case SYS_SETSOCKOPT: err = sys_setsockopt(a0, a1, a[2], (char __user *)a[3], a[4]); break; case SYS_GETSOCKOPT: err = sys_getsockopt(a0, a1, a[2], (char __user *)a[3], (int __user *)a[4]); break; case SYS_SENDMSG: err = sys_sendmsg(a0, (struct msghdr __user *) a1, a[2]); break; case SYS_RECVMSG: err = sys_recvmsg(a0, (struct msghdr __user *) a1, a[2]); break; default: err = -EINVAL; break; } return err; } #endif /* __ARCH_WANT_SYS_SOCKETCALL */ /* * This function is called by a protocol handler that wants to * advertise its address family, and have it linked into the * SOCKET module. */ /* 注册一个网络协议 */ int sock_register(struct net_proto_family *ops) { int err; /* 首先看下网络协议是否符合条件。 这里允许的网络协议列在socket.h中有定义 */ if (ops->family >= NPROTO) { printk(KERN_CRIT "protocol %d >= NPROTO(%d)\n", ops->family, NPROTO); return -ENOBUFS; } net_family_write_lock(); err = -EEXIST; if (net_families[ops->family] == NULL) { /* 不允许重新注册,感觉这里代码比较粗糙 */ net_families[ops->family]=ops; err = 0; } net_family_write_unlock(); printk(KERN_INFO "NET: Registered protocol family %d\n", ops->family); return err; } /* * This function is called by a protocol handler that wants to * remove its address family, and have it unlinked from the * SOCKET module. */ /* 从Linux中解除注册一个网络协议 */ int sock_unregister(int family) { if (family < 0 || family >= NPROTO) return -1; net_family_write_lock() net_families[family]=NULL;/* 直接把对应的指针清除即可 */ net_family_write_unlock(); printk(KERN_INFO "NET: Unregistered protocol family %d\n", family); return 0; } extern void sk_init(void); /* 整个网络的初始化函数 */ void __init sock_init(void) { /* * Initialize sock SLAB cache. */ /* 初始化sk的cache,这里sk是TCP/IP的管理实体,绝大多数网络协议都是基于TCP/IP,因此需要多个实体 */ sk_init(); #ifdef SLAB_SKB /* * Initialize skbuff SLAB cache */ /* 初始化skbuffer 的cache */ skb_init(); #endif /* * Initialize the protocols module. */ /* 在Linux中注册一个文件节点 */ init_inodecache(); register_filesystem(&sock_fs_type); sock_mnt = kern_mount(&sock_fs_type); /* The real protocol initialization is performed when * do_initcalls is run. */ #ifdef CONFIG_NETFILTER netfilter_init(); #endif } /* 如果启用了proc,这里打印下proc信息 */ #ifdef CONFIG_PROC_FS void socket_seq_show(struct seq_file *seq) { int cpu; int counter = 0; for (cpu = 0; cpu < NR_CPUS; cpu++) counter += per_cpu(sockets_in_use, cpu); /* It can be negative, by the way. 8) */ if (counter < 0) counter = 0; seq_printf(seq, "sockets: used %d\n", counter); } #endif /* CONFIG_PROC_FS */ /* ABI emulation layers need these two */ EXPORT_SYMBOL(move_addr_to_kernel); EXPORT_SYMBOL(move_addr_to_user); EXPORT_SYMBOL(sock_create); EXPORT_SYMBOL(sock_create_kern); EXPORT_SYMBOL(sock_create_lite); EXPORT_SYMBOL(sock_map_fd); EXPORT_SYMBOL(sock_recvmsg); EXPORT_SYMBOL(sock_register); EXPORT_SYMBOL(sock_release); EXPORT_SYMBOL(sock_sendmsg); EXPORT_SYMBOL(sock_unregister); EXPORT_SYMBOL(sock_wake_async); EXPORT_SYMBOL(sockfd_lookup); EXPORT_SYMBOL(kernel_sendmsg); EXPORT_SYMBOL(kernel_recvmsg);
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