Support for socket-descriptor marshalling
This patch adds prinicipal support for transmitting socket descriptors as RPC payload. Socket descriptors are handled by the linux-specific implementation of the capability marshalling and unmarshalling functions in 'ipc.h'. The 'Message' type in 'src/platform/linux_socket.h' has been extended to carry multiple descriptors in a single message. Unfortuately, we hit a problem (and potential show stopper) here: lx_sendmsg failed with -109 in lx_call() The error code corresponds to ETOOMANYREFS. There is only one place in the Linux kernel where this error code is used (net/unix/af_unix.c). The code for 'unix_attach_fds()' suggests that there is a limit with regard to the maximum number of references for a given Unix domain socket. When the error occurs, core and init are running. The socket of core's server entrypoint is present in the '/proc/pid/fd' of those processes 8 times. The error occurs when core tries to perform an RPC to the entrypoint to perform 'Ram_session::transfer_quota()' (base/include/base/child.h at line 248).
This commit is contained in:
Norman Feske
parent
8b343d7e1a
commit
ca4f574f4c
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@ -0,0 +1,65 @@
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/*
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* \brief Linux-specific supplements to the IPC framework
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* \author Norman Feske
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* \date 2012-07-26
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*/
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/*
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* Copyright (C) 2012 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__BASE__IPC_H_
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#define _INCLUDE__BASE__IPC_H_
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#include <base/ipc_generic.h>
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#include <base/snprintf.h>
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extern "C" int raw_write_str(const char *str);
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extern "C" void wait_for_continue(void);
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#define PRAWW(fmt, ...) \
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do { \
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char str[128]; \
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Genode::snprintf(str, sizeof(str), \
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ESC_ERR fmt ESC_END "\n", ##__VA_ARGS__); \
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raw_write_str(str); \
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} while (0)
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inline void Genode::Ipc_ostream::_marshal_capability(Genode::Native_capability const &cap)
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{
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PRAWW("_marshal_capability called: local_name=%ld, tid=%ld, socket=%d",
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cap.local_name(), cap.dst().tid, cap.dst().socket);
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_write_to_buf(cap.local_name());
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_write_to_buf(cap.dst().tid);
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if (cap.valid()) {
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PRAWW("append_cap");
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_snd_msg->append_cap(cap.dst().socket);
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}
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}
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inline void Genode::Ipc_istream::_unmarshal_capability(Genode::Native_capability &cap)
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{
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long local_name = 0;
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long tid = 0;
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int socket = -1;
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_read_from_buf(local_name);
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_read_from_buf(tid);
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bool const cap_valid = (tid != 0);
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if (cap_valid)
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socket = _rcv_msg->read_cap();
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cap = Native_capability(Cap_dst_policy::Dst(tid, socket), local_name);
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}
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#endif /* _INCLUDE__BASE__IPC_H_ */
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@ -21,10 +21,30 @@ namespace Genode {
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*/
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class Msgbuf_base
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{
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public:
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enum { MAX_CAPS_PER_MSG = 8 };
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protected:
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/*
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* Capabilities (file descriptors) to be transferred
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*/
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int _caps[MAX_CAPS_PER_MSG];
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Genode::size_t _used_caps;
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Genode::size_t _read_cap_index;
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/**
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* Maximum size of plain-data message payload
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*/
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Genode::size_t _size;
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char _msg_start[]; /* symbol marks start of message buffer data */
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/**
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* Actual size of plain-data message payload
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*/
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Genode::size_t _used_size;
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char _msg_start[]; /* symbol marks start of message buffer data */
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/*
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* No member variables are allowed beyond this point!
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@ -34,6 +54,8 @@ namespace Genode {
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char buf[];
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Msgbuf_base() { reset_caps(); }
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/**
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* Return size of message buffer
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*/
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@ -43,6 +65,36 @@ namespace Genode {
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* Return address of message buffer
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*/
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inline void *addr() { return &_msg_start[0]; };
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void reset_caps() { _used_caps = 0; _read_cap_index = 0; }
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bool append_cap(int cap)
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{
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if (_used_caps == MAX_CAPS_PER_MSG)
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return false;
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_caps[_used_caps++] = cap;
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return true;
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}
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int read_cap()
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{
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if (_read_cap_index == _used_caps)
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return -1;
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return _caps[_read_cap_index++];
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}
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size_t used_caps() const { return _used_caps; }
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int cap(unsigned index) const
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{
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return index < _used_caps ? _caps[index] : -1;
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}
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size_t used_size() const { return _used_size; }
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void used_size(size_t used_size) { _used_size = used_size; }
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};
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@ -92,9 +92,10 @@ void Ipc_istream::_wait()
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Ipc_istream::Ipc_istream(Msgbuf_base *rcv_msg)
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: Ipc_unmarshaller(rcv_msg->buf, rcv_msg->size()),
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Native_capability(Dst(lx_gettid(), -1), 0),
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_rcv_msg(rcv_msg)
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:
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Ipc_unmarshaller(rcv_msg->buf, rcv_msg->size()),
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Native_capability(Dst(lx_gettid(), -1), 0),
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_rcv_msg(rcv_msg)
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{ }
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@ -115,15 +116,16 @@ void Ipc_client::_prepare_next_call()
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/* prepare response buffer */
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_read_offset = sizeof(long);
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_snd_msg->reset_caps();
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}
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void Ipc_client::_call()
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{
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if (Ipc_ostream::_dst.valid()) {
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lx_call(Ipc_ostream::_dst.dst().tid,
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_snd_msg->buf, _write_offset,
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_rcv_msg->buf, _rcv_msg->size());
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_snd_msg->used_size(_write_offset);
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lx_call(Ipc_ostream::_dst.dst().tid, *_snd_msg, *_rcv_msg);
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}
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_prepare_next_call();
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}
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@ -153,6 +155,9 @@ void Ipc_server::_prepare_next_reply_wait()
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/* leave space for exc code at the beginning of the msgbuf */
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_write_offset += align_natural(sizeof(int));
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/* reset capability slots of send message buffer */
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_snd_msg->reset_caps();
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}
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@ -161,7 +166,7 @@ void Ipc_server::_wait()
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_reply_needed = true;
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try {
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int const reply_socket = lx_wait(_rcv_cs, _rcv_msg->buf, _rcv_msg->size());
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int const reply_socket = lx_wait(_rcv_cs, *_rcv_msg);
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/*
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* Remember reply capability
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@ -185,7 +190,8 @@ void Ipc_server::_wait()
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void Ipc_server::_reply()
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{
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try {
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lx_reply(Ipc_ostream::_dst.dst().socket, _snd_msg->buf, _write_offset);
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_snd_msg->used_size(_write_offset);
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lx_reply(Ipc_ostream::_dst.dst().socket, *_snd_msg);
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} catch (Ipc_error) { }
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_prepare_next_reply_wait();
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@ -195,8 +201,10 @@ void Ipc_server::_reply()
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void Ipc_server::_reply_wait()
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{
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/* when first called, there was no request yet */
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if (_reply_needed)
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lx_reply(Ipc_ostream::_dst.dst().socket, _snd_msg->buf, _write_offset);
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if (_reply_needed) {
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_snd_msg->used_size(_write_offset);
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lx_reply(Ipc_ostream::_dst.dst().socket, *_snd_msg);
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}
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_wait();
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}
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@ -231,5 +239,9 @@ Ipc_server::Ipc_server(Msgbuf_base *snd_msg, Msgbuf_base *rcv_msg)
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if (thread)
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thread->tid().is_ipc_server = true;
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/* override capability initialization performed by 'Ipc_istream' */
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*static_cast<Native_capability *>(this) =
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Native_capability(Native_capability::Dst(lx_gettid(), _rcv_cs), 0);
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_prepare_next_reply_wait();
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}
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@ -57,16 +57,22 @@ namespace {
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*/
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struct Message
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{
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public:
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enum { MAX_SDS_PER_MSG = Genode::Msgbuf_base::MAX_CAPS_PER_MSG };
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private:
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msghdr _msg;
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sockaddr_un _addr;
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iovec _iovec;
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char _cmsg_buf[CMSG_SPACE(sizeof(int))];
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char _cmsg_buf[CMSG_SPACE(MAX_SDS_PER_MSG*sizeof(int))];
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unsigned _num_sds;
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public:
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Message(long server_thread_id = -1)
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Message(long server_thread_id = -1) : _num_sds(0)
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{
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memset(&_msg, 0, sizeof(_msg));
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@ -77,6 +83,18 @@ namespace {
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_msg.msg_name = &_addr;
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_msg.msg_namelen = sizeof(_addr);
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}
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/* initialize control message */
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struct cmsghdr *cmsg;
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_msg.msg_control = _cmsg_buf;
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_msg.msg_controllen = sizeof(_cmsg_buf); /* buffer space available */
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_msg.msg_flags |= MSG_CMSG_CLOEXEC;
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cmsg = CMSG_FIRSTHDR(&_msg);
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cmsg->cmsg_len = CMSG_LEN(0);
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cmsg->cmsg_level = SOL_SOCKET;
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cmsg->cmsg_type = SCM_RIGHTS;
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_msg.msg_controllen = cmsg->cmsg_len; /* actual cmsg length */
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}
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msghdr * msg() { return &_msg; }
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_iovec.iov_len = buffer_len;
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}
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/**
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* Prepare slot for socket sending/reception
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*
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* Note, if this function is not called sockets are not accepted on
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* 'recvmsg' and, therefore, do not occupy local file descriptors.
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*/
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void prepare_reply_socket_slot()
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void marshal_socket(int sd)
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{
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/* initialize control message */
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struct cmsghdr *cmsg;
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*((int *)CMSG_DATA((cmsghdr *)_cmsg_buf) + _num_sds) = sd;
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_msg.msg_control = _cmsg_buf;
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_msg.msg_controllen = sizeof(_cmsg_buf); /* buffer space available */
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_msg.msg_flags |= MSG_CMSG_CLOEXEC;
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cmsg = CMSG_FIRSTHDR(&_msg);
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cmsg->cmsg_len = CMSG_LEN(sizeof(int));
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cmsg->cmsg_level = SOL_SOCKET;
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cmsg->cmsg_type = SCM_RIGHTS;
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_num_sds++;
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struct cmsghdr *cmsg = CMSG_FIRSTHDR(&_msg);
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cmsg->cmsg_len = CMSG_LEN(_num_sds*sizeof(int));
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_msg.msg_controllen = cmsg->cmsg_len; /* actual cmsg length */
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}
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void reply_socket(int sd)
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void accept_sockets(int num_sds)
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{
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if (!_msg.msg_control) {
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PRAW("reply-socket slot not prepared");
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throw Genode::Ipc_error();
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}
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*(int *)CMSG_DATA((cmsghdr *)_cmsg_buf) = sd;
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struct cmsghdr *cmsg = CMSG_FIRSTHDR(&_msg);
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cmsg->cmsg_len = CMSG_LEN(num_sds*sizeof(int));
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_msg.msg_controllen = cmsg->cmsg_len; /* actual cmsg length */
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}
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int reply_socket() const
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int unmarshal_socket()
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{
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if (!_msg.msg_control) {
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PRAW("reply-socket slot not prepared");
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throw Genode::Ipc_error();
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}
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int ret = *((int *)CMSG_DATA((cmsghdr *)_cmsg_buf) + _num_sds);
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return *(int *)CMSG_DATA((cmsghdr *)_cmsg_buf);
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_num_sds++;
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return ret;
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}
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/* XXX only for debugging */
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int socket_at_index(int index)
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{
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return *((int *)CMSG_DATA((cmsghdr *)_cmsg_buf) + index);
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}
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unsigned num_sockets() const
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{
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struct cmsghdr *cmsg = CMSG_FIRSTHDR(&_msg);
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if (!cmsg)
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return 0;
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return (cmsg->cmsg_len - CMSG_ALIGN(sizeof(cmsghdr)))/sizeof(int);
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}
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};
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@ -170,8 +190,8 @@ static int lx_server_socket(Genode::Thread_base *thread)
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* Utility: Send request to server and wait for reply
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*/
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static void lx_call(long thread_id,
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void *send_buf, Genode::size_t send_buf_len,
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void *recv_buf, Genode::size_t recv_buf_len)
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Genode::Msgbuf_base &send_msgbuf,
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Genode::Msgbuf_base &recv_msgbuf)
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{
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int ret;
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@ -184,29 +204,62 @@ static void lx_call(long thread_id,
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ret = lx_socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0, reply_channel);
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if (ret < 0) {
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PRAW("lx_socketpair failed with %d", ret);
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/* XXX */ wait_for_continue();
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throw Genode::Ipc_error();
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}
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send_msg.prepare_reply_socket_slot();
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send_msg.reply_socket(reply_channel[REMOTE_SOCKET]);
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send_msg.buffer(send_buf, send_buf_len);
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/* assemble message */
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/* marshal reply capability */
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send_msg.marshal_socket(reply_channel[REMOTE_SOCKET]);
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/* marshal capabilities contained in 'send_msgbuf' */
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if (send_msgbuf.used_caps() > 0)
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PRAW("lx_call: marshal %d caps:", send_msgbuf.used_caps());
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for (unsigned i = 0; i < send_msgbuf.used_caps(); i++) {
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PRAW(" sd[%d]: %d", i, send_msgbuf.cap(i));
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send_msg.marshal_socket(lx_dup(send_msgbuf.cap(i)));
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}
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send_msg.buffer(send_msgbuf.buf, send_msgbuf.used_size());
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ret = lx_sendmsg(reply_channel[LOCAL_SOCKET], send_msg.msg(), 0);
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if (ret < 0) {
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PRAW("lx_sendmsg failed with %d in lx_call()", ret);
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while (1);
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/* XXX */ wait_for_continue();
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throw Genode::Ipc_error();
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}
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Message recv_msg;
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recv_msg.accept_sockets(Message::MAX_SDS_PER_MSG);
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recv_msg.buffer(recv_buf, recv_buf_len);
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recv_msg.buffer(recv_msgbuf.buf, recv_msgbuf.size());
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ret = lx_recvmsg(reply_channel[LOCAL_SOCKET], recv_msg.msg(), 0);
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if (ret < 0) {
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PRAW("lx_recvmsg failed with %d in lx_call()", ret);
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/* XXX */ wait_for_continue();
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throw Genode::Ipc_error();
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}
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/*
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* 'lx_recvmsg()' returns the number of bytes received. remember this value
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* in 'Genode::Msgbuf_base'
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*
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* XXX revisit whether we really need this information
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*/
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recv_msgbuf.used_size(ret);
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if (recv_msg.num_sockets() > 0) {
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PRAW("lx_call: got %d sockets in reply", recv_msg.num_sockets());
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for (unsigned i = 0; i < recv_msg.num_sockets(); i++) {
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PRAW(" sd[%d]: %d", i, recv_msg.socket_at_index(i));
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lx_close(recv_msg.socket_at_index(i));
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}
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}
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/* destroy reply channel */
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lx_close(reply_channel[LOCAL_SOCKET]);
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lx_close(reply_channel[REMOTE_SOCKET]);
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@ -219,22 +272,46 @@ static void lx_call(long thread_id,
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* \return socket descriptor of reply capability
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*/
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static int lx_wait(Genode::Native_connection_state &cs,
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void *buf, Genode::size_t buf_len)
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Genode::Msgbuf_base &recv_msgbuf)
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{
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int ret;
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Message msg;
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msg.prepare_reply_socket_slot();
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msg.buffer(buf, buf_len);
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msg.accept_sockets(Message::MAX_SDS_PER_MSG);
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msg.buffer(recv_msgbuf.buf, recv_msgbuf.size());
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ret = lx_recvmsg(cs, msg.msg(), 0);
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int ret = lx_recvmsg(cs, msg.msg(), 0);
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if (ret < 0) {
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PRAW("lx_recvmsg failed with %d in lx_wait()", ret);
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/* XXX */ wait_for_continue();
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throw Genode::Ipc_error();
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}
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return msg.reply_socket();
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/*
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* 'lx_recvmsg()' returned message size, keep it in 'recv_msgbuf'.
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*
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* XXX revisit whether this information is actually needed.
|
||||
*/
|
||||
recv_msgbuf.used_size(ret);
|
||||
|
||||
|
||||
if (msg.num_sockets() > 1) {
|
||||
PRAW("lx_wait: got %d sockets from wait", msg.num_sockets());
|
||||
for (unsigned i = 0; i < msg.num_sockets(); i++) {
|
||||
PRAW(" sd[%d]: %d", i, msg.socket_at_index(i));
|
||||
|
||||
/* don't close reply channel */
|
||||
if (i > 0)
|
||||
lx_close(msg.socket_at_index(i));
|
||||
}
|
||||
}
|
||||
|
||||
int reply_socket = msg.unmarshal_socket();
|
||||
|
||||
/*
|
||||
* Copy-out additional sds from msg to recv_msgbuf
|
||||
*/
|
||||
|
||||
return reply_socket;
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -242,15 +319,13 @@ static int lx_wait(Genode::Native_connection_state &cs,
|
|||
* Utility: Send reply to client
|
||||
*/
|
||||
static void lx_reply(int reply_socket,
|
||||
void *buf, Genode::size_t buf_len)
|
||||
Genode::Msgbuf_base &send_msgbuf)
|
||||
{
|
||||
int ret;
|
||||
|
||||
Message msg;
|
||||
|
||||
msg.buffer(buf, buf_len);
|
||||
msg.buffer(send_msgbuf.buf, send_msgbuf.used_size());
|
||||
|
||||
ret = lx_sendmsg(reply_socket, msg.msg(), 0);
|
||||
int ret = lx_sendmsg(reply_socket, msg.msg(), 0);
|
||||
if (ret < 0)
|
||||
PRAW("lx_sendmsg failed with %d in lx_reply()", ret);
|
||||
|
||||
|
|
|
|||
|
|
@ -64,6 +64,12 @@ inline int lx_close(int fd)
|
|||
}
|
||||
|
||||
|
||||
inline int lx_dup(int fd)
|
||||
{
|
||||
return lx_syscall(SYS_dup, fd);
|
||||
}
|
||||
|
||||
|
||||
inline int lx_unlink(const char *fname)
|
||||
{
|
||||
return lx_syscall(SYS_unlink, fname);
|
||||
|
|
|
|||
Loading…
Reference in New Issue