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LibCore: Implement LocalSocket send_fd() and receive_fd() on Linux

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We use a combination of SCM_RIGHTS and fcntl(FD_CLOEXEC) to implement
the equivalent functionality from SerenityOS.
This commit is contained in:
Andreas Kling 2022-10-05 14:18:34 +02:00
parent ece1b7422f
commit d652794862
Notes: sideshowbarker 2024-07-17 06:20:55 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/d652794862
1 changed files with 68 additions and 2 deletions
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70
Userland/Libraries/LibCore/Stream.cpp
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@ -561,8 +561,43 @@ ErrorOr<NonnullOwnPtr<LocalSocket>> LocalSocket::adopt_fd(int fd)
ErrorOr<int> LocalSocket::receive_fd(int flags)
{
#ifdef __serenity__
#if defined(AK_OS_SERENITY)
return Core::System::recvfd(m_helper.fd(), flags);
#elif defined(AK_OS_LINUX)
union {
struct cmsghdr cmsghdr;
char control[CMSG_SPACE(sizeof(int))];
} cmsgu {};
char c = 0;
struct iovec iov {
.iov_base = &c,
.iov_len = 1,
};
struct msghdr msg {
.msg_name = NULL,
.msg_namelen = 0,
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cmsgu.control,
.msg_controllen = sizeof(cmsgu.control),
.msg_flags = 0,
};
TRY(Core::System::recvmsg(m_helper.fd(), &msg, 0));
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
if (!cmsg || cmsg->cmsg_len != CMSG_LEN(sizeof(int)))
return Error::from_string_literal("Malformed message when receiving file descriptor");
VERIFY(cmsg->cmsg_level == SOL_SOCKET);
VERIFY(cmsg->cmsg_type == SCM_RIGHTS);
int fd = *((int*)CMSG_DATA(cmsg));
if (flags & O_CLOEXEC) {
auto fd_flags = TRY(Core::System::fcntl(fd, F_GETFD));
TRY(Core::System::fcntl(fd, F_SETFD, fd_flags | FD_CLOEXEC));
}
return fd;
#else
(void)flags;
return Error::from_string_literal("File descriptor passing not supported on this platform");
@ -571,8 +606,39 @@ ErrorOr<int> LocalSocket::receive_fd(int flags)
ErrorOr<void> LocalSocket::send_fd(int fd)
{
#ifdef __serenity__
#if defined(AK_OS_SERENITY)
return Core::System::sendfd(m_helper.fd(), fd);
#elif defined(AK_OS_LINUX)
char c = 'F';
struct iovec iov {
.iov_base = &c,
.iov_len = sizeof(c)
};
union {
struct cmsghdr cmsghdr;
char control[CMSG_SPACE(sizeof(int))];
} cmsgu {};
struct msghdr msg {
.msg_name = NULL,
.msg_namelen = 0,
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cmsgu.control,
.msg_controllen = sizeof(cmsgu.control),
.msg_flags = 0,
};
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
*((int*)CMSG_DATA(cmsg)) = fd;
TRY(Core::System::sendmsg(m_helper.fd(), &msg, 0));
return {};
#else
(void)fd;
return Error::from_string_literal("File descriptor passing not supported on this platform");