On Mon, Sep 30, 2019 at 3:13 PM Josh Hunt <joh...@akamai.com> wrote:
>
> Prior to this change an application sending <= 1MSS worth of data and
> enabling UDP GSO would fail if the system had SW GSO enabled, but the
> same send would succeed if HW GSO offload is enabled. In addition to this
> inconsistency the error in the SW GSO case does not get back to the
> application if sending out of a real device so the user is unaware of this
> failure.
>
> With this change we only perform GSO if the # of segments is > 1 even
> if the application has enabled segmentation. I've also updated the
> relevant udpgso selftests.
>
> Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT")
> Signed-off-by: Josh Hunt <joh...@akamai.com>
> ---
> net/ipv4/udp.c | 5 +++--
> net/ipv6/udp.c | 5 +++--
> tools/testing/selftests/net/udpgso.c | 16 ++++------------
> 3 files changed, 10 insertions(+), 16 deletions(-)
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index be98d0b8f014..ac0baf947560 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -821,6 +821,7 @@ static int udp_send_skb(struct sk_buff *skb, struct
> flowi4 *fl4,
> int is_udplite = IS_UDPLITE(sk);
> int offset = skb_transport_offset(skb);
> int len = skb->len - offset;
> + int datalen = len - sizeof(*uh);
> __wsum csum = 0;
>
> /*
> @@ -832,7 +833,7 @@ static int udp_send_skb(struct sk_buff *skb, struct
> flowi4 *fl4,
> uh->len = htons(len);
> uh->check = 0;
>
> - if (cork->gso_size) {
> + if (cork->gso_size && datalen > cork->gso_size) {
> const int hlen = skb_network_header_len(skb) +
> sizeof(struct udphdr);
>
So what about the datalen == cork->gso_size case? That would only
generate one segment wouldn't it?
Shouldn't the test really be "datalen < cork->gso_size"? That should
be the only check you need since if gso_size is 0 this statement would
always fail anyway.
Thanks.
- Alex
