* [PATCH net-next] tcp: let tcp_mtu_probe() build headless packets
@ 2023-06-07 21:41 Eric Dumazet
2023-06-09 2:40 ` patchwork-bot+netdevbpf
0 siblings, 1 reply; 2+ messages in thread
From: Eric Dumazet @ 2023-06-07 21:41 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, netdev, eric.dumazet, Eric Dumazet
tcp_mtu_probe() is still copying payload from skbs in the write queue,
using skb_copy_bits(), ignoring potential errors.
Modern TCP stack wants to only deal with payload found in page frags,
as this is a prereq for TCPDirect (host stack might not have access
to the payload)
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/ipv4/tcp_output.c | 60 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 58 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index cfe128b81a010339b486dd6a40b077cee9570d08..f8ce77ce7c3ef783717e60cce03d70aa10a4b9a8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2319,6 +2319,57 @@ static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
return true;
}
+static int tcp_clone_payload(struct sock *sk, struct sk_buff *to,
+ int probe_size)
+{
+ skb_frag_t *lastfrag = NULL, *fragto = skb_shinfo(to)->frags;
+ int i, todo, len = 0, nr_frags = 0;
+ const struct sk_buff *skb;
+
+ if (!sk_wmem_schedule(sk, to->truesize + probe_size))
+ return -ENOMEM;
+
+ skb_queue_walk(&sk->sk_write_queue, skb) {
+ const skb_frag_t *fragfrom = skb_shinfo(skb)->frags;
+
+ if (skb_headlen(skb))
+ return -EINVAL;
+
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, fragfrom++) {
+ if (len >= probe_size)
+ goto commit;
+ todo = min_t(int, skb_frag_size(fragfrom),
+ probe_size - len);
+ len += todo;
+ if (lastfrag &&
+ skb_frag_page(fragfrom) == skb_frag_page(lastfrag) &&
+ skb_frag_off(fragfrom) == skb_frag_off(lastfrag) +
+ skb_frag_size(lastfrag)) {
+ skb_frag_size_add(lastfrag, todo);
+ continue;
+ }
+ if (unlikely(nr_frags == MAX_SKB_FRAGS))
+ return -E2BIG;
+ skb_frag_page_copy(fragto, fragfrom);
+ skb_frag_off_copy(fragto, fragfrom);
+ skb_frag_size_set(fragto, todo);
+ nr_frags++;
+ lastfrag = fragto++;
+ }
+ }
+commit:
+ WARN_ON_ONCE(len != probe_size);
+ for (i = 0; i < nr_frags; i++)
+ skb_frag_ref(to, i);
+
+ skb_shinfo(to)->nr_frags = nr_frags;
+ to->truesize += probe_size;
+ to->len += probe_size;
+ to->data_len += probe_size;
+ __skb_header_release(to);
+ return 0;
+}
+
/* Create a new MTU probe if we are ready.
* MTU probe is regularly attempting to increase the path MTU by
* deliberately sending larger packets. This discovers routing
@@ -2395,9 +2446,15 @@ static int tcp_mtu_probe(struct sock *sk)
return -1;
/* We're allowed to probe. Build it now. */
- nskb = tcp_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
+ nskb = tcp_stream_alloc_skb(sk, 0, GFP_ATOMIC, false);
if (!nskb)
return -1;
+
+ /* build the payload, and be prepared to abort if this fails. */
+ if (tcp_clone_payload(sk, nskb, probe_size)) {
+ consume_skb(nskb);
+ return -1;
+ }
sk_wmem_queued_add(sk, nskb->truesize);
sk_mem_charge(sk, nskb->truesize);
@@ -2415,7 +2472,6 @@ static int tcp_mtu_probe(struct sock *sk)
len = 0;
tcp_for_write_queue_from_safe(skb, next, sk) {
copy = min_t(int, skb->len, probe_size - len);
- skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
if (skb->len <= copy) {
/* We've eaten all the data from this skb.
--
2.41.0.rc0.172.g3f132b7071-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH net-next] tcp: let tcp_mtu_probe() build headless packets
2023-06-07 21:41 [PATCH net-next] tcp: let tcp_mtu_probe() build headless packets Eric Dumazet
@ 2023-06-09 2:40 ` patchwork-bot+netdevbpf
0 siblings, 0 replies; 2+ messages in thread
From: patchwork-bot+netdevbpf @ 2023-06-09 2:40 UTC (permalink / raw)
To: Eric Dumazet; +Cc: davem, kuba, pabeni, simon.horman, netdev, eric.dumazet
Hello:
This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:
On Wed, 7 Jun 2023 21:41:13 +0000 you wrote:
> tcp_mtu_probe() is still copying payload from skbs in the write queue,
> using skb_copy_bits(), ignoring potential errors.
>
> Modern TCP stack wants to only deal with payload found in page frags,
> as this is a prereq for TCPDirect (host stack might not have access
> to the payload)
>
> [...]
Here is the summary with links:
- [net-next] tcp: let tcp_mtu_probe() build headless packets
https://git.kernel.org/netdev/net-next/c/736013292e3c
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
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2023-06-09 2:40 ` patchwork-bot+netdevbpf
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