io_uring_prep_sendmsg problem

[Nazar2]

this code works fine and client reads message with recvfrom

struct iovec iov[1];
ssize_t sentCount = 0;
struct msghdr msg;
struct sockaddr_in dest_addr;

dest_addr.sin_family = AF_INET;
dest_addr.sin_port = htons(port);
dest_addr.sin_addr.s_addr = inet_addr(ip);

iov[0].iov_base = data; // Hello from server
iov[0].iov_len = dataLen; // 18

msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_flags = 0;
msg.msg_iov = iov;
msg.msg_iovlen = 1;
msg.msg_name = &dest_addr;
msg.msg_namelen = sizeof(dest_addr);

sentCount = sendmsg(serverSocketUDP, &msg, 0);
printf("%s sent count %zd\n", __func__, sentCount); // 18

this code gives -14 in cqe->res (Bad address)
request is of type request_t and it exists and not erased after code executed and I already did the same with io_uring_prep_recvmsg, io_uring_prep_write, io_uring_prep_cancel, io_uring_prep_timeout_remove, io_uring_prep_close, io_uring_prep_read, io_uring_prep_accept and it works fine and no problems

memcpy(&request->iov[0], data, dataLen); // Hello from server
request->iov[0].iov_len = dataLen; // 18

memset(&request->udp_message_write, 0, sizeof(request->udp_message_write));
memset(&request->client_addr_write, 0, sizeof(request->client_addr_write));

request->client_addr_write.sin_family = AF_INET;
request->client_addr_write.sin_port = htons(port);
request->client_addr_write.sin_addr.s_addr = inet_addr(ip);

request->udp_message_write.msg_control = NULL;
request->udp_message_write.msg_controllen = 0;
request->udp_message_write.msg_flags = 0;
request->udp_message_write.msg_iov = request->iov;
request->udp_message_write.msg_iovlen = 1;
request->udp_message_write.msg_name = &request->client_addr_write;
request->udp_message_write.msg_namelen = sizeof(request->client_addr_write);

io_uring_prep_sendmsg(sqe, serverSocketUDP, &request->udp_message_write, 0);
io_uring_sqe_set_data(sqe, request);

what is wrong with the code above?

[krisman]

Can you share the full code? No idea what request_t is.

this code gives -14 in cqe->res (Bad address)

This means you are passing bad pointers to the kernel. you can try using gdb to print your request right before the io_uring_prep_sendmsg and checking what you are passing wrong.

memcpy(&request->iov[0], data, dataLen); // Hello from server

This looks fishy. iov is an iovec, so it should receive a pointer to the data in iov->iov_base. Looks like you are corrupting the iovec and the following 10bytes, IIUC. Should be:

request->iov[0].iov_base = data;

[Nazar2]

thank you for pointing on iov->iov_base that was my mistake. I'll try to place some variables in local storage to not to use request_t just for testing and see if it helps

[Nazar2]

The problem was with storing iov_base. Need a separate variable to store that data.