On Tue, Oct 8, 2024 at 2:55 PM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote: > > Allow the guest to reuse the hash value to make receive steering > consistent between the host and guest, and to save hash computation. > > Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> I wonder if this would cause overhead when hash reporting is not enabled? > --- > Documentation/networking/tuntap.rst | 7 +++ > drivers/net/Kconfig | 1 + > drivers/net/tap.c | 45 ++++++++++++++-- Tile should be for tap as well or is this just for tun? > drivers/net/tun.c | 46 ++++++++++++---- > drivers/net/tun_vnet.h | 102 +++++++++++++++++++++++++++++++----- > include/linux/if_tap.h | 2 + > include/uapi/linux/if_tun.h | 48 +++++++++++++++++ > 7 files changed, 223 insertions(+), 28 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/Kconfig b/drivers/net/Kconfig > index 9920b3a68ed1..e2a7bd703550 100644 > --- a/drivers/net/Kconfig > +++ b/drivers/net/Kconfig > @@ -395,6 +395,7 @@ config TUN > tristate "Universal TUN/TAP device driver support" > depends on INET > select CRC32 > + select SKB_EXTENSIONS Then we need this for macvtap at least as well? > help > TUN/TAP provides packet reception and transmission for user space > programs. It can be viewed as a simple Point-to-Point or Ethernet > diff --git a/drivers/net/tap.c b/drivers/net/tap.c > index 9a34ceed0c2c..5e2fbe63ca47 100644 > --- a/drivers/net/tap.c > +++ b/drivers/net/tap.c > @@ -179,6 +179,16 @@ static void tap_put_queue(struct tap_queue *q) > sock_put(&q->sk); > } > > +static struct virtio_net_hash *tap_add_hash(struct sk_buff *skb) > +{ > + return (struct virtio_net_hash *)skb->cb; Any reason that tap uses skb->cb but not skb extensions? (And is it safe to use that without cloning?) > +} > + > +static const struct virtio_net_hash *tap_find_hash(const struct sk_buff *skb) > +{ > + return (const struct virtio_net_hash *)skb->cb; > +} > + > /* > * Select a queue based on the rxq of the device on which this packet > * arrived. If the incoming device is not mq, calculate a flow hash > @@ -189,6 +199,7 @@ static void tap_put_queue(struct tap_queue *q) > static struct tap_queue *tap_get_queue(struct tap_dev *tap, > struct sk_buff *skb) > { > + struct flow_keys_basic keys_basic; > struct tap_queue *queue = NULL; > /* Access to taps array is protected by rcu, but access to numvtaps > * isn't. Below we use it to lookup a queue, but treat it as a hint > @@ -198,15 +209,32 @@ static struct tap_queue *tap_get_queue(struct tap_dev *tap, > int numvtaps = READ_ONCE(tap->numvtaps); > __u32 rxq; > > + *tap_add_hash(skb) = (struct virtio_net_hash) { .report = VIRTIO_NET_HASH_REPORT_NONE }; > + > if (!numvtaps) > goto out; > > if (numvtaps == 1) > goto single; > > + if (!skb->l4_hash && !skb->sw_hash) { > + struct flow_keys keys; > + > + skb_flow_dissect_flow_keys(skb, &keys, FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL); > + rxq = flow_hash_from_keys(&keys); > + keys_basic = (struct flow_keys_basic) { > + .control = keys.control, > + .basic = keys.basic > + }; > + } else { > + skb_flow_dissect_flow_keys_basic(NULL, skb, &keys_basic, NULL, 0, 0, 0, > + FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL); > + rxq = skb->hash; > + } > + > /* Check if we can use flow to select a queue */ > - rxq = skb_get_hash(skb); > if (rxq) { > + tun_vnet_hash_report(&tap->vnet_hash, skb, &keys_basic, rxq, tap_add_hash); > queue = rcu_dereference(tap->taps[rxq % numvtaps]); > goto out; > } > @@ -713,15 +741,16 @@ static ssize_t tap_put_user(struct tap_queue *q, > int total; > > if (q->flags & IFF_VNET_HDR) { > - struct virtio_net_hdr vnet_hdr; > + struct virtio_net_hdr_v1_hash vnet_hdr; > > vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz); > > - ret = tun_vnet_hdr_from_skb(q->flags, NULL, skb, &vnet_hdr); > + ret = tun_vnet_hdr_from_skb(vnet_hdr_len, q->flags, NULL, skb, > + tap_find_hash, &vnet_hdr); > if (ret < 0) > goto done; > > - ret = tun_vnet_hdr_put(vnet_hdr_len, iter, &vnet_hdr); > + ret = tun_vnet_hdr_put(vnet_hdr_len, iter, &vnet_hdr, ret); > if (ret < 0) > goto done; > } > @@ -1025,7 +1054,13 @@ static long tap_ioctl(struct file *file, unsigned int cmd, > return ret; > > default: > - return tun_vnet_ioctl(&q->vnet_hdr_sz, &q->flags, cmd, sp); > + rtnl_lock(); > + tap = rtnl_dereference(q->tap); > + ret = tun_vnet_ioctl(&q->vnet_hdr_sz, &q->flags, > + tap ? &tap->vnet_hash : NULL, -EINVAL, > + cmd, sp); > + rtnl_unlock(); > + return ret; > } > } > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index dd8799d19518..27308417b834 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -209,6 +209,7 @@ struct tun_struct { > struct bpf_prog __rcu *xdp_prog; > struct tun_prog __rcu *steering_prog; > struct tun_prog __rcu *filter_prog; > + struct tun_vnet_hash vnet_hash; > struct ethtool_link_ksettings link_ksettings; > /* init args */ > struct file *file; > @@ -451,6 +452,16 @@ static inline void tun_flow_save_rps_rxhash(struct tun_flow_entry *e, u32 hash) > e->rps_rxhash = hash; > } > > +static struct virtio_net_hash *tun_add_hash(struct sk_buff *skb) > +{ > + return skb_ext_add(skb, SKB_EXT_TUN_VNET_HASH); > +} > + > +static const struct virtio_net_hash *tun_find_hash(const struct sk_buff *skb) > +{ > + return skb_ext_find(skb, SKB_EXT_TUN_VNET_HASH); > +} > + > /* We try to identify a flow through its rxhash. The reason that > * we do not check rxq no. is because some cards(e.g 82599), chooses > * the rxq based on the txq where the last packet of the flow comes. As > @@ -459,12 +470,17 @@ static inline void tun_flow_save_rps_rxhash(struct tun_flow_entry *e, u32 hash) > */ > static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb) > { > + struct flow_keys keys; > + struct flow_keys_basic keys_basic; > struct tun_flow_entry *e; > u32 txq, numqueues; > > numqueues = READ_ONCE(tun->numqueues); > > - txq = __skb_get_hash_symmetric(skb); > + memset(&keys, 0, sizeof(keys)); > + skb_flow_dissect(skb, &flow_keys_dissector_symmetric, &keys, 0); > + > + txq = flow_hash_from_keys(&keys); > e = tun_flow_find(&tun->flows[tun_hashfn(txq)], txq); > if (e) { > tun_flow_save_rps_rxhash(e, txq); > @@ -473,6 +489,13 @@ static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb) > txq = reciprocal_scale(txq, numqueues); > } > > + keys_basic = (struct flow_keys_basic) { > + .control = keys.control, > + .basic = keys.basic > + }; > + tun_vnet_hash_report(&tun->vnet_hash, skb, &keys_basic, skb->l4_hash ? skb->hash : txq, > + tun_add_hash); Is using txq required when not l4_hash is required by the virtio-spec? > + > return txq; > } > > @@ -1990,10 +2013,8 @@ static ssize_t tun_put_user_xdp(struct tun_struct *tun, > size_t total; > > if (tun->flags & IFF_VNET_HDR) { > - struct virtio_net_hdr gso = { 0 }; > - > vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz); > - ret = tun_vnet_hdr_put(vnet_hdr_sz, iter, &gso); > + ret = tun_vnet_hdr_put(vnet_hdr_sz, iter, NULL, 0); > if (ret < 0) > return ret; > } > @@ -2018,7 +2039,6 @@ static ssize_t tun_put_user(struct tun_struct *tun, > int vlan_offset = 0; > int vlan_hlen = 0; > int vnet_hdr_sz = 0; > - int ret; > > if (skb_vlan_tag_present(skb)) > vlan_hlen = VLAN_HLEN; > @@ -2043,13 +2063,15 @@ static ssize_t tun_put_user(struct tun_struct *tun, > } > > if (vnet_hdr_sz) { > - struct virtio_net_hdr gso; > + struct virtio_net_hdr_v1_hash gso; > + int ret; > > - ret = tun_vnet_hdr_from_skb(tun->flags, tun->dev, skb, &gso); > + ret = tun_vnet_hdr_from_skb(vnet_hdr_sz, tun->flags, tun->dev, skb, > + tun_find_hash, &gso); > if (ret < 0) > goto done; > > - ret = tun_vnet_hdr_put(vnet_hdr_sz, iter, &gso); > + ret = tun_vnet_hdr_put(vnet_hdr_sz, iter, &gso, ret); > if (ret < 0) > goto done; > } > @@ -3055,9 +3077,10 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd, > goto unlock; > } > > - ret = -EBADFD; > - if (!tun) > + if (!tun) { > + ret = tun_vnet_ioctl(NULL, NULL, NULL, -EBADFD, cmd, argp); This seems not elegant (passing three NULL pointers). Any reason we can't just modify __tun_chr_ioctl() instead of introducing things like tun_vnet_ioctl()? > goto unlock; > + } > > netif_info(tun, drv, tun->dev, "tun_chr_ioctl cmd %u\n", cmd); > > @@ -3256,7 +3279,8 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd, > break; > > default: > - ret = tun_vnet_ioctl(&tun->vnet_hdr_sz, &tun->flags, cmd, argp); > + ret = tun_vnet_ioctl(&tun->vnet_hdr_sz, &tun->flags, > + &tun->vnet_hash, -EINVAL, cmd, argp); > } > > if (do_notify) > diff --git a/drivers/net/tun_vnet.h b/drivers/net/tun_vnet.h > index c40bde0fdf8c..589a97dd7d02 100644 > --- a/drivers/net/tun_vnet.h > +++ b/drivers/net/tun_vnet.h > @@ -6,6 +6,9 @@ > #define TUN_VNET_LE 0x80000000 > #define TUN_VNET_BE 0x40000000 > > +typedef struct virtio_net_hash *(*tun_vnet_hash_add)(struct sk_buff *); > +typedef const struct virtio_net_hash *(*tun_vnet_hash_find)(const struct sk_buff *); > + > static inline bool tun_vnet_legacy_is_little_endian(unsigned int flags) > { > return !(IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) && (flags & TUN_VNET_BE)) && > @@ -59,18 +62,31 @@ static inline __virtio16 cpu_to_tun_vnet16(unsigned int flags, u16 val) > } > > static inline long tun_vnet_ioctl(int *sz, unsigned int *flags, > - unsigned int cmd, int __user *sp) > + struct tun_vnet_hash *hash, long fallback, > + unsigned int cmd, void __user *argp) > { > + static const struct tun_vnet_hash cap = { > + .flags = TUN_VNET_HASH_REPORT, > + .types = VIRTIO_NET_SUPPORTED_HASH_TYPES > + }; Let's find a way to reuse virtio-net uAPI instead of introducing new stuff to stress the management layer. > + struct tun_vnet_hash hash_buf; > + int __user *sp = argp; > int s; > > switch (cmd) { > case TUNGETVNETHDRSZ: > + if (!sz) > + return -EBADFD; > + > s = *sz; > if (put_user(s, sp)) > return -EFAULT; > return 0; > > case TUNSETVNETHDRSZ: > + if (!sz) > + return -EBADFD; > + > if (get_user(s, sp)) > return -EFAULT; > if (s < (int)sizeof(struct virtio_net_hdr)) > @@ -80,12 +96,18 @@ static inline long tun_vnet_ioctl(int *sz, unsigned int *flags, > return 0; > > case TUNGETVNETLE: > + if (!flags) > + return -EBADFD; > + > s = !!(*flags & TUN_VNET_LE); > if (put_user(s, sp)) > return -EFAULT; > return 0; > > case TUNSETVNETLE: > + if (!flags) > + return -EBADFD; > + > if (get_user(s, sp)) > return -EFAULT; > if (s) > @@ -95,16 +117,56 @@ static inline long tun_vnet_ioctl(int *sz, unsigned int *flags, > return 0; > > case TUNGETVNETBE: > + if (!flags) > + return -EBADFD; > + > return tun_vnet_get_be(*flags, sp); > > case TUNSETVNETBE: > + if (!flags) > + return -EBADFD; > + > return tun_vnet_set_be(flags, sp); > > + case TUNGETVNETHASHCAP: > + return copy_to_user(argp, &cap, sizeof(cap)) ? -EFAULT : 0; > + > + case TUNSETVNETHASH: > + if (!hash) > + return -EBADFD; > + > + if (copy_from_user(&hash_buf, argp, sizeof(hash_buf))) > + return -EFAULT; > + > + *hash = hash_buf; > + return 0; > + > default: > - return -EINVAL; > + return fallback; > } > } > > +static inline void tun_vnet_hash_report(const struct tun_vnet_hash *hash, > + struct sk_buff *skb, > + const struct flow_keys_basic *keys, > + u32 value, > + tun_vnet_hash_add vnet_hash_add) > +{ > + struct virtio_net_hash *report; > + > + if (!(hash->flags & TUN_VNET_HASH_REPORT)) > + return; > + > + report = vnet_hash_add(skb); > + if (!report) > + return; > + > + *report = (struct virtio_net_hash) { > + .report = virtio_net_hash_report(hash->types, keys), > + .value = value > + }; > +} > + > static inline int tun_vnet_hdr_get(int sz, unsigned int flags, > struct iov_iter *from, > struct virtio_net_hdr *hdr) > @@ -130,15 +192,15 @@ static inline int tun_vnet_hdr_get(int sz, unsigned int flags, > } > > static inline int tun_vnet_hdr_put(int sz, struct iov_iter *iter, > - const struct virtio_net_hdr *hdr) > + const void *hdr, int content_sz) > { > if (iov_iter_count(iter) < sz) > return -EINVAL; > > - if (copy_to_iter(hdr, sizeof(*hdr), iter) != sizeof(*hdr)) > + if (copy_to_iter(hdr, content_sz, iter) != content_sz) > return -EFAULT; > > - if (iov_iter_zero(sz - sizeof(*hdr), iter) != sz - sizeof(*hdr)) > + if (iov_iter_zero(sz - content_sz, iter) != sz - content_sz) > return -EFAULT; > > return 0; > @@ -151,32 +213,48 @@ static inline int tun_vnet_hdr_to_skb(unsigned int flags, > return virtio_net_hdr_to_skb(skb, hdr, tun_vnet_is_little_endian(flags)); > } > > -static inline int tun_vnet_hdr_from_skb(unsigned int flags, > +static inline int tun_vnet_hdr_from_skb(int sz, unsigned int flags, > const struct net_device *dev, > const struct sk_buff *skb, > - struct virtio_net_hdr *hdr) > + tun_vnet_hash_find vnet_hash_find, > + struct virtio_net_hdr_v1_hash *hdr) > { > int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0; > + const struct virtio_net_hash *report = sz < sizeof(struct virtio_net_hdr_v1_hash) ? > + NULL : vnet_hash_find(skb); > + int content_sz; > + > + if (report) { > + content_sz = sizeof(struct virtio_net_hdr_v1_hash); > + > + *hdr = (struct virtio_net_hdr_v1_hash) { > + .hdr = { .num_buffers = __cpu_to_virtio16(true, 1) }, > + .hash_value = cpu_to_le32(report->value), > + .hash_report = cpu_to_le16(report->report) > + }; > + } else { > + content_sz = sizeof(struct virtio_net_hdr); > + } > > - if (virtio_net_hdr_from_skb(skb, hdr, > + if (virtio_net_hdr_from_skb(skb, (struct virtio_net_hdr *)hdr, > tun_vnet_is_little_endian(flags), true, > vlan_hlen)) { > struct skb_shared_info *sinfo = skb_shinfo(skb); > > if (net_ratelimit()) { > netdev_err(dev, "unexpected GSO type: 0x%x, gso_size %d, hdr_len %d\n", > - sinfo->gso_type, tun_vnet16_to_cpu(flags, hdr->gso_size), > - tun_vnet16_to_cpu(flags, hdr->hdr_len)); > + sinfo->gso_type, tun_vnet16_to_cpu(flags, hdr->hdr.gso_size), > + tun_vnet16_to_cpu(flags, hdr->hdr.hdr_len)); > print_hex_dump(KERN_ERR, "tun: ", > DUMP_PREFIX_NONE, > 16, 1, skb->head, > - min(tun_vnet16_to_cpu(flags, hdr->hdr_len), 64), true); > + min(tun_vnet16_to_cpu(flags, hdr->hdr.hdr_len), 64), true); > } > WARN_ON_ONCE(1); > return -EINVAL; > } > > - return 0; > + return content_sz; > } > > #endif /* TUN_VNET_H */ > diff --git a/include/linux/if_tap.h b/include/linux/if_tap.h > index 553552fa635c..5bbb343a6dba 100644 > --- a/include/linux/if_tap.h > +++ b/include/linux/if_tap.h > @@ -4,6 +4,7 @@ > > #include <net/sock.h> > #include <linux/skb_array.h> > +#include <uapi/linux/if_tun.h> > > struct file; > struct socket; > @@ -43,6 +44,7 @@ struct tap_dev { > int numqueues; > netdev_features_t tap_features; > int minor; > + struct tun_vnet_hash vnet_hash; > > void (*update_features)(struct tap_dev *tap, netdev_features_t features); > void (*count_tx_dropped)(struct tap_dev *tap); > diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h > index 287cdc81c939..d11e79b4e0dc 100644 > --- a/include/uapi/linux/if_tun.h > +++ b/include/uapi/linux/if_tun.h > @@ -62,6 +62,34 @@ > #define TUNSETCARRIER _IOW('T', 226, int) > #define TUNGETDEVNETNS _IO('T', 227) > > +/** > + * define TUNGETVNETHASHCAP - ioctl to get virtio_net hashing capability. > + * > + * The argument is a pointer to &struct tun_vnet_hash which will store the > + * maximal virtio_net hashing configuration. > + */ > +#define TUNGETVNETHASHCAP _IOR('T', 228, struct tun_vnet_hash) > + > +/** > + * define TUNSETVNETHASH - ioctl to configure virtio_net hashing > + * > + * The argument is a pointer to &struct tun_vnet_hash. > + * > + * The %TUN_VNET_HASH_REPORT flag set with this ioctl will be effective only > + * after calling the %TUNSETVNETHDRSZ ioctl with a number greater than or equal > + * to the size of &struct virtio_net_hdr_v1_hash. I think we don't need & here. > + * > + * The members added to the legacy header by %TUN_VNET_HASH_REPORT flag will > + * always be little-endian. > + * > + * This ioctl results in %EBADFD if the underlying device is deleted. It affects > + * all queues attached to the same device. > + * > + * This ioctl currently has no effect on XDP packets and packets with > + * queue_mapping set by TC. This needs to be fixed? > + */ > +#define TUNSETVNETHASH _IOW('T', 229, struct tun_vnet_hash) > + > /* TUNSETIFF ifr flags */ > #define IFF_TUN 0x0001 > #define IFF_TAP 0x0002 > @@ -115,4 +143,24 @@ struct tun_filter { > __u8 addr[][ETH_ALEN]; > }; > > +/** > + * define TUN_VNET_HASH_REPORT - Request virtio_net hash reporting for vhost > + */ > +#define TUN_VNET_HASH_REPORT 0x0001 > + > +/** > + * struct tun_vnet_hash - virtio_net hashing configuration > + * @flags: > + * Bitmask consists of %TUN_VNET_HASH_REPORT and %TUN_VNET_HASH_RSS Could we reuse TUNGETIFF by introduce new IFF_XXX stuffs? > + * @pad: > + * Should be filled with zero before passing to %TUNSETVNETHASH > + * @types: > + * Bitmask of allowed hash types What are they? > + */ > +struct tun_vnet_hash { > + __u16 flags; > + __u8 pad[2]; > + __u32 types; > +}; > + > #endif /* _UAPI__IF_TUN_H */ > > -- > 2.46.2 > Thanks