[RFC v2 07/19] ipv6/udp: add support msgdr::msg_ubuf

[Pavel Begunkov <asml.silence@gmail.com>]

Make ipv6/udp to use ubuf_info passed in struct msghdr if it was
specified.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 net/ipv6/ip6_output.c | 49 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 37 insertions(+), 12 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 2f044a49afa8..822e3894dd3b 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1452,6 +1452,7 @@ static int __ip6_append_data(struct sock *sk,
 	unsigned int maxnonfragsize, headersize;
 	unsigned int wmem_alloc_delta = 0;
 	bool paged, extra_uref = false;
+	bool zc = false;
 
 	skb = skb_peek_tail(queue);
 	if (!skb) {
@@ -1516,17 +1517,37 @@ static int __ip6_append_data(struct sock *sk,
 	    rt->dst.dev->features & (NETIF_F_IPV6_CSUM | NETIF_F_HW_CSUM))
 		csummode = CHECKSUM_PARTIAL;
 
-	if (flags & MSG_ZEROCOPY && length && sock_flag(sk, SOCK_ZEROCOPY)) {
-		uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
-		if (!uarg)
-			return -ENOBUFS;
-		extra_uref = !skb_zcopy(skb);	/* only ref on new uarg */
-		if (rt->dst.dev->features & NETIF_F_SG &&
-		    csummode == CHECKSUM_PARTIAL) {
-			paged = true;
-		} else {
-			uarg->zerocopy = 0;
-			skb_zcopy_set(skb, uarg, &extra_uref);
+	if ((flags & MSG_ZEROCOPY) && length) {
+		struct msghdr *msg = from;
+
+		if (getfrag == ip_generic_getfrag && msg->msg_ubuf) {
+			uarg = msg->msg_ubuf;
+			if (skb_zcopy(skb) && uarg != skb_zcopy(skb))
+				return -EINVAL;
+
+			if (rt->dst.dev->features & NETIF_F_SG &&
+				csummode == CHECKSUM_PARTIAL) {
+				paged = true;
+				zc = true;
+			} else {
+				/* Drop uarg if can't zerocopy, callers should
+				 * be able to handle it.
+				 */
+				uarg = NULL;
+			}
+		} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
+			uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
+			if (!uarg)
+				return -ENOBUFS;
+			extra_uref = !skb_zcopy(skb);	/* only ref on new uarg */
+			if (rt->dst.dev->features & NETIF_F_SG &&
+			    csummode == CHECKSUM_PARTIAL) {
+				paged = true;
+				zc = true;
+			} else {
+				uarg->zerocopy = 0;
+				skb_zcopy_set(skb, uarg, &extra_uref);
+			}
 		}
 	}
 
@@ -1717,9 +1738,13 @@ static int __ip6_append_data(struct sock *sk,
 				err = -EFAULT;
 				goto error;
 			}
-		} else if (!uarg || !uarg->zerocopy) {
+		} else if (!zc) {
 			int i = skb_shinfo(skb)->nr_frags;
 
+			if (skb_shinfo(skb)->flags & SKBFL_MANAGED_FRAGS) {
+				err = -EFAULT;
+				goto error;
+			}
 			err = -ENOMEM;
 			if (!sk_page_frag_refill(sk, pfrag))
 				goto error;
-- 
2.34.1