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| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2019-02-19 19:53:02 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-02-19 21:56:05 +0100 |
| commit | 74e31ca850c1cddeca03503171dd145b6ce293b6 (patch) | |
| tree | 069ba2607739490c6dcd75cb47da15b7105995b4 /net/core | |
| parent | 568f196756ad9fe2b49c46bbf6a9de1b190438b4 (diff) | |
| download | lwn-74e31ca850c1cddeca03503171dd145b6ce293b6.tar.gz lwn-74e31ca850c1cddeca03503171dd145b6ce293b6.zip | |
bpf: add skb->queue_mapping write access from tc clsact
The skb->queue_mapping already have read access, via __sk_buff->queue_mapping.
This patch allow BPF tc qdisc clsact write access to the queue_mapping via
tc_cls_act_is_valid_access. Also handle that the value NO_QUEUE_MAPPING
is not allowed.
It is already possible to change this via TC filter action skbedit
tc-skbedit(8). Due to the lack of TC examples, lets show one:
# tc qdisc add dev ixgbe1 clsact
# tc filter add dev ixgbe1 ingress matchall action skbedit queue_mapping 5
# tc filter list dev ixgbe1 ingress
The most common mistake is that XPS (Transmit Packet Steering) takes
precedence over setting skb->queue_mapping. XPS is configured per DEVICE
via /sys/class/net/DEVICE/queues/tx-*/xps_cpus via a CPU hex mask. To
disable set mask=00.
The purpose of changing skb->queue_mapping is to influence the selection of
the net_device "txq" (struct netdev_queue), which influence selection of
the qdisc "root_lock" (via txq->qdisc->q.lock) and txq->_xmit_lock. When
using the MQ qdisc the txq->qdisc points to different qdiscs and associated
locks, and HARD_TX_LOCK (txq->_xmit_lock), allowing for CPU scalability.
Due to lack of TC examples, lets show howto attach clsact BPF programs:
# tc qdisc add dev ixgbe2 clsact
# tc filter add dev ixgbe2 egress bpf da obj XXX_kern.o sec tc_qmap2cpu
# tc filter list dev ixgbe2 egress
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index b584cb42a803..85749f6ec789 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6279,6 +6279,7 @@ static bool tc_cls_act_is_valid_access(int off, int size, case bpf_ctx_range(struct __sk_buff, tc_classid): case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]): case bpf_ctx_range(struct __sk_buff, tstamp): + case bpf_ctx_range(struct __sk_buff, queue_mapping): break; default: return false; @@ -6683,9 +6684,18 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type, break; case offsetof(struct __sk_buff, queue_mapping): - *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, - bpf_target_off(struct sk_buff, queue_mapping, 2, - target_size)); + if (type == BPF_WRITE) { + *insn++ = BPF_JMP_IMM(BPF_JGE, si->src_reg, NO_QUEUE_MAPPING, 1); + *insn++ = BPF_STX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct sk_buff, + queue_mapping, + 2, target_size)); + } else { + *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct sk_buff, + queue_mapping, + 2, target_size)); + } break; case offsetof(struct __sk_buff, vlan_present): |