by Ammar Faizi

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Subject: Re: [RFC PATCH v3 3/3] io_uring: Add `sendto(2)` and `recvfrom(2)` support

On 1/7/22 3:33 PM, Praveen Kumar wrote:
> On 07-01-2022 02:08, Ammar Faizi wrote:
>> On Thu, 6 Jan 2022 at 23:01:59 +0530, Praveen Kumar <[email protected]> wrote:
>>> On 30-12-2021 23:22, Ammar Faizi wrote:
>>>> This adds sendto(2) and recvfrom(2) support for io_uring.
>>>>
>>>> New opcodes:
>>>> IORING_OP_SENDTO
>>>> IORING_OP_RECVFROM
>>>>
>>>> Cc: Nugra <[email protected]>
>>>> Tested-by: Nugra <[email protected]>
>>>> Link: https://github.com/axboe/liburing/issues/397
>>>> Signed-off-by: Ammar Faizi <[email protected]>
>>>> ---
>>>>
>>>> v3:
>>>> - Fix build error when CONFIG_NET is undefined should be done in
>>>> the first patch, not this patch.
>>>>
>>>> - Add Tested-by tag from Nugra.
>>>>
>>>> v2:
>>>> - In `io_recvfrom()`, mark the error check of `move_addr_to_user()`
>>>> call as unlikely.
>>>>
>>>> - Fix build error when CONFIG_NET is undefined.
>>>>
>>>> - Added Nugra to CC list (tester).
>>>> ---
>>>> fs/io_uring.c | 80 +++++++++++++++++++++++++++++++++--
>>>> include/uapi/linux/io_uring.h | 2 +
>>>> 2 files changed, 78 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>>> index 7adcb591398f..3726958f8f58 100644
>>>> --- a/fs/io_uring.c
>>>> +++ b/fs/io_uring.c
>>>> @@ -575,7 +575,15 @@ struct io_sr_msg {
>>>> union {
>>>> struct compat_msghdr __user *umsg_compat;
>>>> struct user_msghdr __user *umsg;
>>>> - void __user *buf;
>>>> +
>>>> + struct {
>>>> + void __user *buf;
>>>> + struct sockaddr __user *addr;
>>>> + union {
>>>> + int sendto_addr_len;
>>>> + int __user *recvfrom_addr_len;
>>>> + };
>>>> + };
>>>> };
>>>> int msg_flags;
>>>> int bgid;
>>>> @@ -1133,6 +1141,19 @@ static const struct io_op_def io_op_defs[] = {
>>>> .needs_file = 1
>>>> },
>>>> [IORING_OP_GETXATTR] = {},
>>>> + [IORING_OP_SENDTO] = {
>>>> + .needs_file = 1,
>>>> + .unbound_nonreg_file = 1,
>>>> + .pollout = 1,
>>>> + .audit_skip = 1,
>>>> + },
>>>> + [IORING_OP_RECVFROM] = {
>>>> + .needs_file = 1,
>>>> + .unbound_nonreg_file = 1,
>>>> + .pollin = 1,
>>>> + .buffer_select = 1,
>>>> + .audit_skip = 1,
>>>> + },
>>>> };
>>>>
>>>> /* requests with any of those set should undergo io_disarm_next() */
>>>> @@ -5216,12 +5237,24 @@ static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>> if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
>>>> return -EINVAL;
>>>>
>>>> + /*
>>>> + * For IORING_OP_SEND{,TO}, the assignment to @sr->umsg
>>>> + * is equivalent to an assignment to @sr->buf.
>>>> + */
>>>> sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
>>>> +
>>>> sr->len = READ_ONCE(sqe->len);
>>>> sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;
>>>> if (sr->msg_flags & MSG_DONTWAIT)
>>>> req->flags |= REQ_F_NOWAIT;
>>>>
>>>> + if (req->opcode == IORING_OP_SENDTO) {
>>>> + sr->addr = u64_to_user_ptr(READ_ONCE(sqe->addr2));
>>>> + sr->sendto_addr_len = READ_ONCE(sqe->addr3);
>>>> + } else {
>>>> + sr->addr = (struct sockaddr __user *) NULL;
>>>
>>> Let's have sendto_addr_len = 0
>>
>> Will do in the RFC v5.
>>
>>>
>>>> + }
>>>> +
>>>> #ifdef CONFIG_COMPAT
>>>> if (req->ctx->compat)
>>>> sr->msg_flags |= MSG_CMSG_COMPAT;
>>>> @@ -5275,6 +5308,7 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
>>>>
>>>> static int io_sendto(struct io_kiocb *req, unsigned int issue_flags)
>>>> {
>>>> + struct sockaddr_storage address;
>>>> struct io_sr_msg *sr = &req->sr_msg;
>>>> struct msghdr msg;
>>>> struct iovec iov;
>>>> @@ -5291,10 +5325,20 @@ static int io_sendto(struct io_kiocb *req, unsigned int issue_flags)
>>>> if (unlikely(ret))
>>>> return ret;
>>>>
>>>> - msg.msg_name = NULL;
>>>> +
>>>> msg.msg_control = NULL;
>>>> msg.msg_controllen = 0;
>>>> - msg.msg_namelen = 0;
>>>> + if (sr->addr) {
>>>> + ret = move_addr_to_kernel(sr->addr, sr->sendto_addr_len,
>>>> + &address);
>>>> + if (unlikely(ret < 0))
>>>> + goto fail;
>>>> + msg.msg_name = (struct sockaddr *) &address;
>>>> + msg.msg_namelen = sr->sendto_addr_len;
>>>> + } else {
>>>> + msg.msg_name = NULL;
>>>> + msg.msg_namelen = 0;
>>>> + }
>>>>
>>>> flags = req->sr_msg.msg_flags;
>>>> if (issue_flags & IO_URING_F_NONBLOCK)
>>>> @@ -5309,6 +5353,7 @@ static int io_sendto(struct io_kiocb *req, unsigned int issue_flags)
>>>> return -EAGAIN;
>>>> if (ret == -ERESTARTSYS)
>>>> ret = -EINTR;
>>>> + fail:
>>>> req_set_fail(req);
>>>
>>> I think there is a problem with "fail" goto statement. Not getting
>>> full clarity on this change. With latest kernel, I see
>>> req_set_fail(req) inside if check, which I don't see here. Can you
>>> please resend the patch on latest kernel version. Thanks.
>>
>> I will send the v5 on top of "for-next" branch in Jens' tree soon.
>>
>> That is already inside an "if check" anyway. We go to that label when
>> the move_addr_to_kernel() fails (most of the time it is -EFAULT or
>> -EINVAL).
>>
>> That part looks like this (note the if check before the goto):
>> ----------------------------------------------------------------------
>> msg.msg_control = NULL;
>> msg.msg_controllen = 0;
>> if (sr->addr) {
>> ret = move_addr_to_kernel(sr->addr, sr->sendto_addr_len,
>> &address);
>> if (unlikely(ret < 0))
>> goto fail;
>> msg.msg_name = (struct sockaddr *) &address;
>> msg.msg_namelen = sr->sendto_addr_len;
>> } else {
>> msg.msg_name = NULL;
>> msg.msg_namelen = 0;
>> }
>>
>> flags = req->sr_msg.msg_flags;
>> if (issue_flags & IO_URING_F_NONBLOCK)
>> flags |= MSG_DONTWAIT;
>> if (flags & MSG_WAITALL)
>> min_ret = iov_iter_count(&msg.msg_iter);
>>
>> msg.msg_flags = flags;
>> ret = sock_sendmsg(sock, &msg);
>> if (ret < min_ret) {
>> if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK))
>> return -EAGAIN;
>> if (ret == -ERESTARTSYS)
>> ret = -EINTR;
>> fail:
>
> Thanks for sending this. IMO this goto label should be just before
> the "if (ret < min_ret)" statement.

AFAICT, error returned by move_addr_to_kernel are only -EFAULT and -EINVAL,
so the check against -EAGAIN and -ERESTARTSYS is unnecessary for that
case. We can skip that.

RFC v4 here (rebased on top of "for-next" Jens' tree):
https://lore.kernel.org/io-uring/[email protected]/T/

>
>> req_set_fail(req);
>> }
>> __io_req_complete(req, issue_flags, ret, 0);
>> return 0;
>> ----------------------------------------------------------------------
>>
>>>> }
>>>> __io_req_complete(req, issue_flags, ret, 0);
>>>> @@ -5427,13 +5472,25 @@ static int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>> if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
>>>> return -EINVAL;
>>>>
>>>> + /*
>>>> + * For IORING_OP_RECV{,FROM}, the assignment to @sr->umsg
>>>> + * is equivalent to an assignment to @sr->buf.
>>>> + */
>>>> sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
>>>> +
>>>> sr->len = READ_ONCE(sqe->len);
>>>> sr->bgid = READ_ONCE(sqe->buf_group);
>>>> sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;
>>>> if (sr->msg_flags & MSG_DONTWAIT)
>>>> req->flags |= REQ_F_NOWAIT;
>>>>
>>>> + if (req->opcode == IORING_OP_RECVFROM) {
>>>> + sr->addr = u64_to_user_ptr(READ_ONCE(sqe->addr2));
>>>> + sr->recvfrom_addr_len = u64_to_user_ptr(READ_ONCE(sqe->addr3));
>>>> + } else {
>>>> + sr->addr = (struct sockaddr __user *) NULL;
>>>
>>> I think recvfrom_addr_len should also be pointed to NULL, instead of
>>> garbage for this case.
>>
>> Will do in the RFC v5.
>>
>>>
>>>> + }
>>>> +
>>>> #ifdef CONFIG_COMPAT
>>>> if (req->ctx->compat)
>>>> sr->msg_flags |= MSG_CMSG_COMPAT;
>>>> @@ -5509,6 +5566,7 @@ static int io_recvfrom(struct io_kiocb *req, unsigned int issue_flags)
>>>> struct iovec iov;
>>>> unsigned flags;
>>>> int ret, min_ret = 0;
>>>> + struct sockaddr_storage address;
>>>> bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
>>>>
>>>> sock = sock_from_file(req->file);
>>>> @@ -5526,7 +5584,7 @@ static int io_recvfrom(struct io_kiocb *req, unsigned int issue_flags)
>>>> if (unlikely(ret))
>>>> goto out_free;
>>>>
>>>> - msg.msg_name = NULL;
>>>> + msg.msg_name = sr->addr ? (struct sockaddr *) &address : NULL;
>>>> msg.msg_control = NULL;
>>>> msg.msg_controllen = 0;
>>>> msg.msg_namelen = 0;
>>>
>>> I think namelen should also be updated ?
>>
>> It doesn't have to be updated. From net/socket.c there is a comment
>> like this:
>>
>> /* We assume all kernel code knows the size of sockaddr_storage */
>> msg.msg_namelen = 0;
>>
>> Full __sys_recvfrom() source code, see here:
>> https://github.com/torvalds/linux/blob/v5.16-rc8/net/socket.c#L2085-L2088
>>
>> I will add the same comment in next series to clarify this one.
>>
>>>
>>>> @@ -5540,6 +5598,16 @@ static int io_recvfrom(struct io_kiocb *req, unsigned int issue_flags)
>>>> min_ret = iov_iter_count(&msg.msg_iter);
>>>>
>>>> ret = sock_recvmsg(sock, &msg, flags);
>>>> +
>>>> + if (ret >= 0 && sr->addr != NULL) {
>>>> + int tmp;
>>>> +
>>>> + tmp = move_addr_to_user(&address, msg.msg_namelen, sr->addr,
>>>> + sr->recvfrom_addr_len);
>>>> + if (unlikely(tmp < 0))
>>>> + ret = tmp;
>>>> + }
>>>> +
>>>> out_free:
>>>> if (ret < min_ret) {
>>>> if (ret == -EAGAIN && force_nonblock)
>>>> @@ -6778,9 +6846,11 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>> case IORING_OP_SYNC_FILE_RANGE:
>>>> return io_sfr_prep(req, sqe);
>>>> case IORING_OP_SENDMSG:
>>>> + case IORING_OP_SENDTO:
>>>> case IORING_OP_SEND:
>>>> return io_sendmsg_prep(req, sqe);
>>>> case IORING_OP_RECVMSG:
>>>> + case IORING_OP_RECVFROM:
>>>> case IORING_OP_RECV:
>>>> return io_recvmsg_prep(req, sqe);
>>>> case IORING_OP_CONNECT:
>>>> @@ -7060,12 +7130,14 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
>>>> case IORING_OP_SENDMSG:
>>>> ret = io_sendmsg(req, issue_flags);
>>>> break;
>>>> + case IORING_OP_SENDTO:
>>>> case IORING_OP_SEND:
>>>> ret = io_sendto(req, issue_flags);
>>>> break;
>>>> case IORING_OP_RECVMSG:
>>>> ret = io_recvmsg(req, issue_flags);
>>>> break;
>>>> + case IORING_OP_RECVFROM:
>>>> case IORING_OP_RECV:
>>>> ret = io_recvfrom(req, issue_flags);
>>>> break;
>>>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>>>> index efc7ac9b3a6b..a360069d1e8e 100644
>>>> --- a/include/uapi/linux/io_uring.h
>>>> +++ b/include/uapi/linux/io_uring.h
>>>> @@ -150,6 +150,8 @@ enum {
>>>> IORING_OP_SETXATTR,
>>>> IORING_OP_FGETXATTR,
>>>> IORING_OP_GETXATTR,
>>>> + IORING_OP_SENDTO,
>>>> + IORING_OP_RECVFROM,
>>>>
>>>> /* this goes last, obviously */
>>>> IORING_OP_LAST,
>>>
>>>
>>> Regards,
>>>
>>> ~Praveen.
>>>
>>
>> Thanks for the review. I will send the RFC v5 soon.
>>
>

--
Ammar Faizi

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