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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