This clarifies a steering eBPF program takes precedence over the other steering algorithms.
Signed-off-by: Akihiko Odaki akihiko.odaki@daynix.com --- Documentation/networking/tuntap.rst | 7 +++++++ drivers/net/tun.c | 28 +++++++++++++++++----------- include/uapi/linux/if_tun.h | 9 +++++++++ 3 files changed, 33 insertions(+), 11 deletions(-)
diff --git a/Documentation/networking/tuntap.rst b/Documentation/networking/tuntap.rst index 4d7087f727be..86b4ae8caa8a 100644 --- a/Documentation/networking/tuntap.rst +++ b/Documentation/networking/tuntap.rst @@ -206,6 +206,13 @@ enable is true we enable it, otherwise we disable it:: return ioctl(fd, TUNSETQUEUE, (void *)&ifr); }
+3.4 Reference +------------- + +``linux/if_tun.h`` defines the interface described below: + +.. kernel-doc:: include/uapi/linux/if_tun.h + Universal TUN/TAP device driver Frequently Asked Question =========================================================
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index d8f4d3e996a7..9133ab9ed3f5 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -476,21 +476,29 @@ static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb) return txq; }
-static u16 tun_ebpf_select_queue(struct tun_struct *tun, struct sk_buff *skb) +static bool tun_ebpf_select_queue(struct tun_struct *tun, struct sk_buff *skb, + u16 *ret) { struct tun_prog *prog; u32 numqueues; - u16 ret = 0; + u32 prog_ret; + + prog = rcu_dereference(tun->steering_prog); + if (!prog) + return false;
numqueues = READ_ONCE(tun->numqueues); - if (!numqueues) - return 0; + if (!numqueues) { + *ret = 0; + return true; + }
- prog = rcu_dereference(tun->steering_prog); - if (prog) - ret = bpf_prog_run_clear_cb(prog->prog, skb); + prog_ret = bpf_prog_run_clear_cb(prog->prog, skb); + if (prog_ret == TUN_STEERINGEBPF_FALLBACK) + return false;
- return ret % numqueues; + *ret = (u16)prog_ret % numqueues; + return true; }
static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb, @@ -500,9 +508,7 @@ static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb, u16 ret;
rcu_read_lock(); - if (rcu_dereference(tun->steering_prog)) - ret = tun_ebpf_select_queue(tun, skb); - else + if (!tun_ebpf_select_queue(tun, skb, &ret)) ret = tun_automq_select_queue(tun, skb); rcu_read_unlock();
diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h index 287cdc81c939..980de74724fc 100644 --- a/include/uapi/linux/if_tun.h +++ b/include/uapi/linux/if_tun.h @@ -115,4 +115,13 @@ struct tun_filter { __u8 addr[][ETH_ALEN]; };
+/** + * define TUN_STEERINGEBPF_FALLBACK - A steering eBPF return value to fall back + * + * A steering eBPF program may return this value to fall back to the steering + * algorithm that should have been used if the program was not set. This allows + * selectively overriding the steering decision. + */ +#define TUN_STEERINGEBPF_FALLBACK -1 + #endif /* _UAPI__IF_TUN_H */