c - 错误: ‘struct msghdr’ has no member named ‘msg_iov’

Question

我正在内核模块中编写unix套接字，当我尝试编译时，出现以下错误:

error: ‘struct msghdr’ has no member named ‘msg_iov’

error: ‘struct msghdr’ has no member named ‘msg_iovlen’

我尝试阅读 msghdr 的实现，但没有找到任何内容。

ret = kernel_recvmsg(sock, msg, vec, BUFFER_SIZE, BUFFER_SIZE, 0);

msg_iov = msg->msg_iov;
msg_iovlen = msg->msg_iovlen;

Answer 1

看来您使用的 Linux 内核 >= 3.19。自 3.19 内核起 struct msghdr分为struct msghdr和struct user_msghdr。

现在struct user_msghdr包含msg_iov和msg_iovlen。但是struct iov_iter必须使用 代替 msg_iov 和 msg_iovlen。

类似于:

struct msghdr msg;
struct iovec iov;
iov.iov_base = buffer;
iov.iov_len  = length;

/* fill in msg */

#if LINUX_VERSION_CODE < KERNEL_VERSION(3,19,0)
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
#else
iov_iter_init(&msg.msg_iter, READ, &iov, 1, length);
#endif

/* ... */
/* call sock_recvmsg() or kernel_recvmsg() */