linux-kernel - [RFC PATCH 5/7] tun: add ioctl code TUNSETHASHPOPULATION

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Date:   Tue, 12 Jan 2021 21:41:41 +0200
From:   Yuri Benditovich <yuri.benditovich@...nix.com>
To:     davem@...emloft.net, kuba@...nel.org, mst@...hat.com,
        jasowang@...hat.com, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org,
        rdunlap@...radead.org, willemb@...gle.com, gustavoars@...nel.org,
        herbert@...dor.apana.org.au, steffen.klassert@...unet.com,
        nogikh@...gle.com, pablo@...filter.org, decui@...rosoft.com,
        cai@....pw, jakub@...udflare.com, elver@...gle.com,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Cc:     yan@...nix.com
Subject: [RFC PATCH 5/7] tun: add ioctl code TUNSETHASHPOPULATION

User mode program calls this ioctl before loading of
BPF program to inform the tun that the BPF program has
extended functionality, i.e. sets hash value and returns
the virtqueue number in the lower 16 bits and the type
of the hash report in the upper 16 bits.

Signed-off-by: Yuri Benditovich <yuri.benditovich@...nix.com>
---
 drivers/net/tun.c           | 12 +++++++++++-
 include/uapi/linux/if_tun.h |  1 +
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 18c1baf1a6c1..45f4f04a4a3e 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -197,6 +197,7 @@ struct tun_struct {
 	struct sock_fprog	fprog;
 	/* protected by rtnl lock */
 	bool			filter_attached;
+	bool                    bpf_populates_hash;
 	u32			msg_enable;
 	spinlock_t lock;
 	struct hlist_head flows[TUN_NUM_FLOW_ENTRIES];
@@ -2765,6 +2766,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 
 		tun->align = NET_SKB_PAD;
 		tun->filter_attached = false;
+		tun->bpf_populates_hash = false;
 		tun->sndbuf = tfile->socket.sk->sk_sndbuf;
 		tun->rx_batched = 0;
 		RCU_INIT_POINTER(tun->steering_prog, NULL);
@@ -2997,7 +2999,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 	struct net *net = sock_net(&tfile->sk);
 	struct tun_struct *tun;
 	void __user* argp = (void __user*)arg;
-	unsigned int ifindex, carrier;
+	unsigned int ifindex, carrier, populate_hash;
 	struct ifreq ifr;
 	kuid_t owner;
 	kgid_t group;
@@ -3298,6 +3300,14 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 		ret = open_related_ns(&net->ns, get_net_ns);
 		break;
 
+	case TUNSETHASHPOPULATION:
+		ret = -EFAULT;
+		if (copy_from_user(&populate_hash, argp, sizeof(populate_hash)))
+			goto unlock;
+		tun->bpf_populates_hash = !!populate_hash;
+		ret = 0;
+		break;
+
 	default:
 		ret = -EINVAL;
 		break;
diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h
index 454ae31b93c7..0fd43533da26 100644
--- a/include/uapi/linux/if_tun.h
+++ b/include/uapi/linux/if_tun.h
@@ -61,6 +61,7 @@
 #define TUNSETFILTEREBPF _IOR('T', 225, int)
 #define TUNSETCARRIER _IOW('T', 226, int)
 #define TUNGETDEVNETNS _IO('T', 227)
+#define TUNSETHASHPOPULATION _IOR('T', 228, int)
 
 /* TUNSETIFF ifr flags */
 #define IFF_TUN		0x0001
-- 
2.17.1