[PATCH net-next v4 09/27] ipv4/udp: support externally provided ubufs

Pavel Begunkov
2022-07-07T11:52:34Z

Teach ipv4/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>
---
net/ipv4/ip_output.c | 44 +++++++++++++++++++++++++++++++-------------
1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 581d1e233260..df7f9dfbe8be 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1017,18 +1017,35 @@ static int __ip_append_data(struct sock *sk,
(!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_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);
+ }
}
}

@@ -1192,13 +1209,14 @@ static int __ip_append_data(struct sock *sk,
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;
--
2.36.1