ipv6/udp: support externally provided ubufs

Teach ipv6/udp how to use external ubuf_info provided in msghdr and
also prepare it for managed frags by sprinkling
skb_zcopy_downgrade_managed() when it could mix managed and not managed
frags.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index fc74ce3ed8cc7974bc83403eb90a76ee0eda8ed7..897ca4f9b791f25dc05026e6535e5d3cab2507a4 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1542,18 +1542,35 @@ emsgsize:
            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;
-                       zc = 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) {
+                       if (skb_zcopy(skb) && msg->msg_ubuf != skb_zcopy(skb))
+                               return -EINVAL;
+
+                       /* Leave uarg NULL if can't zerocopy, callers should
+                        * be able to handle it.
+                        */
+                       if ((rt->dst.dev->features & NETIF_F_SG) &&
+                           csummode == CHECKSUM_PARTIAL) {
+                               paged = true;
+                               zc = true;
+                               uarg = msg->msg_ubuf;
+                       }
+               } 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);
+                       }
                }
        }
 
@@ -1747,13 +1764,14 @@ alloc_new_skb:
                                err = -EFAULT;
                                goto error;
                        }
-               } else if (!uarg || !uarg->zerocopy) {
+               } else if (!zc) {
                        int i = skb_shinfo(skb)->nr_frags;
 
                        err = -ENOMEM;
                        if (!sk_page_frag_refill(sk, pfrag))
                                goto error;
 
+                       skb_zcopy_downgrade_managed(skb);
                        if (!skb_can_coalesce(skb, i, pfrag->page,
                                              pfrag->offset)) {
                                err = -EMSGSIZE;