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Kernel: Support sending filedescriptors with sendmsg(2) and SCM_RIGHTS

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This is necessary to support the wayland protocol.
I also moved the CMSG_* macros to the kernel API since they are used in
both kernel and userspace.
this does not break ntpquery/SCM_TIMESTAMP.
This commit is contained in:
Peter Elliott 2023-02-13 16:01:13 -07:00 • committed by Linus Groh
parent ae5d7f542c
commit f20902deb3
5 changed files with 97 additions and 37 deletions
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61
Kernel/Syscalls/socket.cpp
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@ -4,6 +4,7 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/ByteBuffer.h>
#include <Kernel/FileSystem/OpenFileDescription.h>
#include <Kernel/Net/LocalSocket.h>
#include <Kernel/Process.h>
@ -199,6 +200,24 @@ ErrorOr<FlatPtr> Process::sys$sendmsg(int sockfd, Userspace<const struct msghdr*
Thread::current()->send_signal(SIGPIPE, &Process::current());
return EPIPE;
}
if (msg.msg_controllen > 0) {
// Handle command messages.
auto cmsg_buffer = TRY(ByteBuffer::create_uninitialized(msg.msg_controllen));
TRY(copy_from_user(cmsg_buffer.data(), msg.msg_control, msg.msg_controllen));
msg.msg_control = cmsg_buffer.data();
for (struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg); cmsg != nullptr; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (socket.is_local() && cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
auto& local_socket = static_cast<LocalSocket&>(socket);
int* fds = (int*)CMSG_DATA(cmsg);
size_t nfds = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr))) / sizeof(int);
for (size_t i = 0; i < nfds; ++i) {
TRY(local_socket.sendfd(*description, TRY(open_file_description(fds[i]))));
}
}
}
}
auto data_buffer = TRY(UserOrKernelBuffer::for_user_buffer((u8*)iovs[0].iov_base, iovs[0].iov_len));
while (true) {
@ -267,21 +286,41 @@ ErrorOr<FlatPtr> Process::sys$recvmsg(int sockfd, Userspace<struct msghdr*> user
msg_flags |= MSG_TRUNC;
}
if (socket.wants_timestamp()) {
struct {
cmsghdr cmsg;
timeval timestamp;
} cmsg_timestamp;
socklen_t control_length = sizeof(cmsg_timestamp);
if (msg.msg_controllen < control_length) {
socklen_t current_cmsg_len = 0;
auto try_add_cmsg = [&](int level, int type, void const* data, socklen_t len) -> ErrorOr<bool> {
if (current_cmsg_len + len > msg.msg_controllen) {
msg_flags |= MSG_CTRUNC;
} else {
cmsg_timestamp = { { control_length, SOL_SOCKET, SCM_TIMESTAMP }, timestamp.to_timeval() };
TRY(copy_to_user(msg.msg_control, &cmsg_timestamp, control_length));
return false;
}
TRY(copy_to_user(&user_msg.unsafe_userspace_ptr()->msg_controllen, &control_length));
cmsghdr cmsg = { (socklen_t)CMSG_LEN(len), level, type };
cmsghdr* target = (cmsghdr*)(((char*)msg.msg_control) + current_cmsg_len);
TRY(copy_to_user(target, &cmsg));
TRY(copy_to_user(CMSG_DATA(target), data, len));
current_cmsg_len += CMSG_ALIGN(cmsg.cmsg_len);
return true;
};
if (socket.wants_timestamp()) {
timeval time = timestamp.to_timeval();
TRY(try_add_cmsg(SOL_SOCKET, SCM_TIMESTAMP, &time, sizeof(time)));
}
int space_for_fds = (msg.msg_controllen - current_cmsg_len - sizeof(struct cmsghdr)) / sizeof(int);
if (space_for_fds > 0 && socket.is_local()) {
auto& local_socket = static_cast<LocalSocket&>(socket);
auto descriptions = TRY(local_socket.recvfds(description, space_for_fds));
Vector<int> fdnums;
for (auto& description : descriptions) {
auto fd_allocation = TRY(m_fds.with_exclusive([](auto& fds) { return fds.allocate(); }));
m_fds.with_exclusive([&](auto& fds) { fds[fd_allocation.fd].set(description, 0); });
fdnums.append(fd_allocation.fd);
}
TRY(try_add_cmsg(SOL_SOCKET, SCM_RIGHTS, fdnums.data(), fdnums.size() * sizeof(int)));
}
TRY(copy_to_user(&user_msg.unsafe_userspace_ptr()->msg_controllen, &current_cmsg_len));
TRY(copy_to_user(&user_msg.unsafe_userspace_ptr()->msg_flags, &msg_flags));
return result.value();
}