Re: xdp generic default option
From: Andrii Nakryiko <hidden>
Date: 2020-08-19 20:58:04
Also in:
bpf
On Wed, Aug 19, 2020 at 2:29 AM Lorenzo Bianconi [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Hi Andrii, working on xdp multi-buff I figured out now xdp generic is the default choice if not specified by userspace. In particular after commit 7f0a838254bd ("bpf, xdp: Maintain info on attached XDP BPF programs in net_device"), running the command below, XDP will run in generic mode even if the underlay driver support XDP in native mode: $ip link set dev eth0 xdp obj prog.o $ip link show dev eth0 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 xdpgeneric qdisc mq state UP mode DEFAULT group default qlen 1024 link/ether f0:ad:4e:09:6b:57 brd ff:ff:ff:ff:ff:ff prog/xdp id 1 tag 3b185187f1855c4c jited Is it better to use xdpdrv as default choice if not specified by userspace? doing something like:diff --git a/net/core/dev.c b/net/core/dev.c index a00aa737ce29..1f85880ee412 100644 --- a/net/core/dev.c +++ b/net/core/dev.c@@ -8747,9 +8747,9 @@ static enum bpf_xdp_mode dev_xdp_mode(u32 flags) { if (flags & XDP_FLAGS_HW_MODE) return XDP_MODE_HW; - if (flags & XDP_FLAGS_DRV_MODE) - return XDP_MODE_DRV; - return XDP_MODE_SKB; + if (flags & XDP_FLAGS_SKB_MODE) + return XDP_MODE_SKB; + return XDP_MODE_DRV; }
I think the better way would be to choose XDP_MODE_DRV if ndo_bpf != NULL and XDP_MODE_SKB otherwise. That seems to be matching original behavior, no? It was not my intent to change the behavior, sorry about that. I'll post patch a bit later today.
static bpf_op_t dev_xdp_bpf_op(struct net_device *dev, enum bpf_xdp_mode mode) Regards, Lorenzo