[PATCH net-next] bpf, xdp: move offload check into dev_xdp_install()
From: Jiayuan Chen <jiayuan.chen@linux.dev>
Date: 2026-08-12 06:37:01
Also in:
bpf, lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
bpf_xdp_link_update() calls dev_xdp_install() directly and skips
dev_xdp_attach(), so the checks in dev_xdp_attach() do not run. A user can
make an XDP link with a normal program and then swap in an offloaded or
device-bound program with BPF_LINK_UPDATE, which puts it on the software
path.
dev_xdp_install() is the one place all three paths go through:
"ip link set xdp" and BPF_LINK_CREATE reach it via dev_xdp_attach(), and
BPF_LINK_UPDATE calls it directly. So move the program checks (offloaded,
bound to another device, device-bound in generic mode, native vs generic,
DEVMAP and CPUMAP) there, and keep only the netlink-flag check
(XDP_FLAGS_UPDATE_IF_NOEXIST) in dev_xdp_attach().
Fixes: 026a4c28e1db3 ("bpf, xdp: Implement LINK_UPDATE for BPF XDP link")
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
1. Previous topic: https://lore.kernel.org/netdev/20260811171047.4e6a409c@kernel.org/ (local)
2. Tested with tools/testing/selftests/net/bpf_offload.py and the BPF CI; both pass.
---
net/core/dev.c | 59 ++++++++++++++++++++++++++------------------------
1 file changed, 31 insertions(+), 28 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index fd0b445f5d38..b390c2edfb33 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -10360,6 +10360,37 @@ static int dev_xdp_install(struct net_device *dev, enum bpf_xdp_mode mode, netdev_assert_locked_ops_compat(dev); + if (prog) { + enum bpf_xdp_mode other_mode = mode == XDP_MODE_SKB + ? XDP_MODE_DRV : XDP_MODE_SKB; + bool offload = mode == XDP_MODE_HW; + + if (!offload && dev_xdp_prog(dev, other_mode)) { + NL_SET_ERR_MSG(extack, "Native and generic XDP can't be active at the same time"); + return -EEXIST; + } + if (!offload && bpf_prog_is_offloaded(prog->aux)) { + NL_SET_ERR_MSG(extack, "Using offloaded program without HW_MODE flag is not supported"); + return -EINVAL; + } + if (bpf_prog_is_dev_bound(prog->aux) && !bpf_offload_dev_match(prog, dev)) { + NL_SET_ERR_MSG(extack, "Program bound to different device"); + return -EINVAL; + } + if (bpf_prog_is_dev_bound(prog->aux) && mode == XDP_MODE_SKB) { + NL_SET_ERR_MSG(extack, "Can't attach device-bound programs in generic mode"); + return -EINVAL; + } + if (prog->expected_attach_type == BPF_XDP_DEVMAP) { + NL_SET_ERR_MSG(extack, "BPF_XDP_DEVMAP programs can not be attached to a device"); + return -EINVAL; + } + if (prog->expected_attach_type == BPF_XDP_CPUMAP) { + NL_SET_ERR_MSG(extack, "BPF_XDP_CPUMAP programs can not be attached to a device"); + return -EINVAL; + } + } + if (dev->cfg->hds_config == ETHTOOL_TCP_DATA_SPLIT_ENABLED && prog && !prog->aux->xdp_has_frags) { NL_SET_ERR_MSG(extack, "unable to install XDP to device using tcp-data-split");
@@ -10499,38 +10530,10 @@ static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack new_prog = link->link.prog; if (new_prog) { - bool offload = mode == XDP_MODE_HW; - enum bpf_xdp_mode other_mode = mode == XDP_MODE_SKB - ? XDP_MODE_DRV : XDP_MODE_SKB; - if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) && cur_prog) { NL_SET_ERR_MSG(extack, "XDP program already attached"); return -EBUSY; } - if (!offload && dev_xdp_prog(dev, other_mode)) { - NL_SET_ERR_MSG(extack, "Native and generic XDP can't be active at the same time"); - return -EEXIST; - } - if (!offload && bpf_prog_is_offloaded(new_prog->aux)) { - NL_SET_ERR_MSG(extack, "Using offloaded program without HW_MODE flag is not supported"); - return -EINVAL; - } - if (bpf_prog_is_dev_bound(new_prog->aux) && !bpf_offload_dev_match(new_prog, dev)) { - NL_SET_ERR_MSG(extack, "Program bound to different device"); - return -EINVAL; - } - if (bpf_prog_is_dev_bound(new_prog->aux) && mode == XDP_MODE_SKB) { - NL_SET_ERR_MSG(extack, "Can't attach device-bound programs in generic mode"); - return -EINVAL; - } - if (new_prog->expected_attach_type == BPF_XDP_DEVMAP) { - NL_SET_ERR_MSG(extack, "BPF_XDP_DEVMAP programs can not be attached to a device"); - return -EINVAL; - } - if (new_prog->expected_attach_type == BPF_XDP_CPUMAP) { - NL_SET_ERR_MSG(extack, "BPF_XDP_CPUMAP programs can not be attached to a device"); - return -EINVAL; - } } /* don't call drivers if the effective program didn't change */
--
2.43.0