From d7a7e2d17d9a62f303d00a13aac77c2e778147aa Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josh@tailscale.com>
Date: Tue, 1 Jun 2021 15:53:29 -0700
Subject: [PATCH] move msghdr to Go

---
 net/uring/io_uring.c        | 13 ++-----------
 net/uring/io_uring_linux.go |  5 ++++-
 2 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/net/uring/io_uring.c b/net/uring/io_uring.c
index 164daa0cd..371552bd8 100644
--- a/net/uring/io_uring.c
+++ b/net/uring/io_uring.c
@@ -15,6 +15,7 @@
 // TODO: use fixed buffers? https://unixism.net/loti/tutorial/fixed_buffers.html
 
 typedef struct io_uring go_uring;
+typedef struct msghdr go_msghdr;
 
 // Wait for a completion to be available, fetch the data
 static int receive_into(int sock, struct io_uring *ring, char *ip, uint16_t *port) {
@@ -50,7 +51,6 @@ again:;
 
     free(mhdr->msg_iov);
     free(mhdr->msg_name);
-    free(mhdr);
 
     io_uring_cqe_seen(ring, cqe);
     return n;
@@ -58,17 +58,10 @@ again:;
 
 // submit a recvmsg request via liburing
 // TODO: What recvfrom support arrives, maybe use that instead?
-static int submit_recvmsg_request(int sock, struct io_uring *ring, char *buf, int buflen) {
-    struct msghdr *mhdr = malloc(sizeof(struct msghdr));
-    if (!mhdr) {
-        perror("malloc(msghdr)");
-        return 1;
-    }
-
+static int submit_recvmsg_request(int sock, struct io_uring *ring, struct msghdr *mhdr, char *buf, int buflen) {
     struct iovec *iov = malloc(sizeof(struct iovec));
     if (!iov) {
         perror("malloc(iov)");
-        free(iov);
         return 1;
     }
 
@@ -76,7 +69,6 @@ static int submit_recvmsg_request(int sock, struct io_uring *ring, char *buf, in
     if (!sender) {
         perror("malloc(sender)");
         free(iov);
-        free(mhdr);
         return 1;
     }
 
@@ -84,7 +76,6 @@ static int submit_recvmsg_request(int sock, struct io_uring *ring, char *buf, in
     iov->iov_base = buf;
     iov->iov_len = buflen;
 
-    memset(mhdr, 0, sizeof(*mhdr));
     mhdr->msg_iov = iov;
     mhdr->msg_iovlen = 1;
 
diff --git a/net/uring/io_uring_linux.go b/net/uring/io_uring_linux.go
index 29c401d02..09ad7970c 100644
--- a/net/uring/io_uring_linux.go
+++ b/net/uring/io_uring_linux.go
@@ -9,6 +9,7 @@
 	"fmt"
 	"net"
 	"os"
+	"runtime"
 	"sync"
 	"time"
 	"unsafe"
@@ -69,8 +70,9 @@ func (u *UDPConn) ReadFromNetaddr(buf []byte) (int, netaddr.IPPort, error) {
 	if u.fd == 0 {
 		return 0, netaddr.IPPort{}, errors.New("invalid uring.UDPConn")
 	}
+	mhdr := new(C.go_msghdr)
 	// TODO: eventually separate submitting the request and waiting for the response.
-	errno := C.submit_recvmsg_request(u.fd, u.ptr, (*C.char)(unsafe.Pointer(&buf[0])), C.int(len(buf)))
+	errno := C.submit_recvmsg_request(u.fd, u.ptr, mhdr, (*C.char)(unsafe.Pointer(&buf[0])), C.int(len(buf)))
 	if errno < 0 {
 		return 0, netaddr.IPPort{}, fmt.Errorf("uring.UDPConn recv failed: %v", errno) // TODO: Improve errno
 	}
@@ -82,6 +84,7 @@ func (u *UDPConn) ReadFromNetaddr(buf []byte) (int, netaddr.IPPort, error) {
 		return 0, netaddr.IPPort{}, errors.New("something wrong")
 	}
 	ipp := netaddr.IPPortFrom(netaddr.IPFrom4(*a), uint16(port))
+	runtime.KeepAlive(mhdr)
 	return int(n), ipp, nil
 }