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Message-ID: <a55816a9-073b-c030-f7f8-19588124e08b@antgroup.com>
Date: Thu, 09 Mar 2023 19:59:41 +0800
From: "沈安琪(凛玥)" <amy.saq@...group.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
netdev@...r.kernel.org
Cc: <mst@...hat.com>, <davem@...emloft.net>, <jasowang@...hat.com>,
"谈鉴锋" <henry.tjf@...group.com>
Subject: Re: [PATCH v3] net/packet: support mergeable feature of virtio
在 2023/3/7 下午11:49, Willem de Bruijn 写道:
> 沈安琪(凛玥) wrote:
>> From: Jianfeng Tan <henry.tjf@...group.com>
>>
>> Packet sockets, like tap, can be used as the backend for kernel vhost.
>> In packet sockets, virtio net header size is currently hardcoded to be
>> the size of struct virtio_net_hdr, which is 10 bytes; however, it is not
>> always the case: some virtio features, such as mrg_rxbuf, need virtio
>> net header to be 12-byte long.
>>
>> Mergeable buffers, as a virtio feature, is worthy of supporting: packets
>> that are larger than one-mbuf size will be dropped in vhost worker's
>> handle_rx if mrg_rxbuf feature is not used, but large packets
>> cannot be avoided and increasing mbuf's size is not economical.
>>
>> With this mergeable feature enabled by virtio-user, packet sockets with
>> hardcoded 10-byte virtio net header will parse mac head incorrectly in
>> packet_snd by taking the last two bytes of virtio net header as part of
>> mac header.
>> This incorrect mac header parsing will cause packet to be dropped due to
>> invalid ether head checking in later under-layer device packet receiving.
>>
>> By adding extra field vnet_hdr_sz with utilizing holes in struct
>> packet_sock to record currently used virtio net header size and supporting
>> extra sockopt PACKET_VNET_HDR_SZ to set specified vnet_hdr_sz, packet
>> sockets can know the exact length of virtio net header that virtio user
>> gives.
>> In packet_snd, tpacket_snd and packet_recvmsg, instead of using
>> hardcoded virtio net header size, it can get the exact vnet_hdr_sz from
>> corresponding packet_sock, and parse mac header correctly based on this
>> information to avoid the packets being mistakenly dropped.
>>
>> Besides, has_vnet_hdr field in struct packet_sock is removed since all
>> the information it provides is covered by vnet_hdr_sz field: a packet
>> socket has a vnet header if and only if its vnet_hdr_sz is not zero.
>>
>> Signed-off-by: Jianfeng Tan <henry.tjf@...group.com>
>> Co-developed-by: Anqi Shen <amy.saq@...group.com>
>> Signed-off-by: Anqi Shen <amy.saq@...group.com>
>> ---
>>
>> /*
>> @@ -2310,8 +2310,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
>> netoff = TPACKET_ALIGN(po->tp_hdrlen +
>> (maclen < 16 ? 16 : maclen)) +
>> po->tp_reserve;
>> - if (po->has_vnet_hdr) {
>> - netoff += sizeof(struct virtio_net_hdr);
>> + if (po->vnet_hdr_sz != 0) {
>> + netoff += po->vnet_hdr_sz;
> no need to test != 0 here and elsewhere, just if (po->vnet_hdr_sz)
>
>> do_vnet = true;
>> }
>> macoff = netoff - maclen;
>> @@ -2552,16 +2552,27 @@ static int __packet_snd_vnet_parse(struct virtio_net_hdr *vnet_hdr, size_t len)
>> }
>>
>> static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
>> @@ -2730,6 +2741,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
>> int status = TP_STATUS_AVAILABLE;
>> int hlen, tlen, copylen = 0;
>> long timeo = 0;
>> + int vnet_hdr_sz;
> since po->vnet_hdr_sz is touched in the hot path anyway, initialize
> it here and use the local var everywhere. Else this might race with
> updates too header length.
>>
>> mutex_lock(&po->pg_vec_lock);
>>
>> @@ -2780,7 +2792,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
>> size_max = po->tx_ring.frame_size
>> - (po->tp_hdrlen - sizeof(struct sockaddr_ll));
>>
>> - if ((size_max > dev->mtu + reserve + VLAN_HLEN) && !po->has_vnet_hdr)
>> + if ((size_max > dev->mtu + reserve + VLAN_HLEN) && po->vnet_hdr_sz == 0)
>> size_max = dev->mtu + reserve + VLAN_HLEN;
>>
>> reinit_completion(&po->skb_completion);
>> @@ -2809,10 +2821,11 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
>> status = TP_STATUS_SEND_REQUEST;
>> hlen = LL_RESERVED_SPACE(dev);
>> tlen = dev->needed_tailroom;
>> - if (po->has_vnet_hdr) {
>> + if (po->vnet_hdr_sz != 0) {
>> vnet_hdr = data;
>> - data += sizeof(*vnet_hdr);
>> - tp_len -= sizeof(*vnet_hdr);
>> + vnet_hdr_sz = po->vnet_hdr_sz;
> .. in particularly here, where vnet_hdr_sz is first checked and then copied
> to a local var in a separate step.
>
>> + data += vnet_hdr_sz;
>> + tp_len -= vnet_hdr_sz;
>> if (tp_len < 0 ||
>> __packet_snd_vnet_parse(vnet_hdr, tp_len)) {
>> tp_len = -EINVAL;
>> @@ -2837,7 +2850,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
>> addr, hlen, copylen, &sockc);
>> if (likely(tp_len >= 0) &&
>> tp_len > dev->mtu + reserve &&
>> - !po->has_vnet_hdr &&
>> + (po->vnet_hdr_sz == 0) &&
>> !packet_extra_vlan_len_allowed(dev, skb))
>> tp_len = -EMSGSIZE;
>>
>> @@ -2856,7 +2869,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
>> }
>> }
>>
>> - if (po->has_vnet_hdr) {
>> + if (po->vnet_hdr_sz != 0) {
>> if (virtio_net_hdr_to_skb(skb, vnet_hdr, vio_le())) {
>> tp_len = -EINVAL;
>> goto tpacket_error;
>> @@ -2947,6 +2960,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
>> int offset = 0;
>> struct packet_sock *po = pkt_sk(sk);
>> bool has_vnet_hdr = false;
> remove has_vnet_hdr, which is now superfluous.
>
>> + int vnet_hdr_sz;
>> int hlen, tlen, linear;
>> int extra_len = 0;
>>
>> @@ -2990,8 +3004,9 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
>>
>> if (sock->type == SOCK_RAW)
>> reserve = dev->hard_header_len;
>> - if (po->has_vnet_hdr) {
>> - err = packet_snd_vnet_parse(msg, &len, &vnet_hdr);
>> + if (po->vnet_hdr_sz != 0) {
>> + vnet_hdr_sz = po->vnet_hdr_sz;
> same here
>
>> + err = packet_snd_vnet_parse(msg, &len, &vnet_hdr, vnet_hdr_sz);
>> if (err)
>> goto out_unlock;
>> has_vnet_hdr = true;
>> @@ -3068,7 +3083,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
>> err = virtio_net_hdr_to_skb(skb, &vnet_hdr, vio_le());
>> if (err)
>> goto out_free;
>> - len += sizeof(vnet_hdr);
>> + len += vnet_hdr_sz;
>> virtio_net_hdr_set_proto(skb, &vnet_hdr);
>> }
>>
>> @@ -3451,11 +3466,11 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>
>> packet_rcv_try_clear_pressure(pkt_sk(sk));
>>
>> - if (pkt_sk(sk)->has_vnet_hdr) {
>> - err = packet_rcv_vnet(msg, skb, &len);
>> + if (pkt_sk(sk)->vnet_hdr_sz != 0) {
>> + vnet_hdr_len = pkt_sk(sk)->vnet_hdr_sz;
> and here
>
>> + err = packet_rcv_vnet(msg, skb, &len, vnet_hdr_len);
>> if (err)
>> goto out_free;
>> - vnet_hdr_len = sizeof(struct virtio_net_hdr);
>> }
>>
>> /* You lose any data beyond the buffer you gave. If it worries
>> @@ -3921,8 +3936,10 @@ static void packet_flush_mclist(struct sock *sk)
>> return 0;
>> }
>> case PACKET_VNET_HDR:
>> + case PACKET_VNET_HDR_SZ:
>> {
>> int val;
>> + int hdr_len = 0;
>>
>> if (sock->type != SOCK_RAW)
>> return -EINVAL;
>> @@ -3931,11 +3948,21 @@ static void packet_flush_mclist(struct sock *sk)
>> if (copy_from_sockptr(&val, optval, sizeof(val)))
>> return -EFAULT;
>>
>> + if (optname == PACKET_VNET_HDR_SZ) {
>> + if (val != sizeof(struct virtio_net_hdr) &&
>> + val != sizeof(struct virtio_net_hdr_mrg_rxbuf))
>> + return -EINVAL;
>> + hdr_len = val;
> val == 0 is also a a correct value
>
>> + } else {
>> + if (!!val)
>> + hdr_len = sizeof(struct virtio_net_hdr);
> no need for !! when testing non-zero.
>
> and instead of initializing to zero on initial variable definition:
>
> hdr_len = val ? sizeof(struct virtio_net_hdr) : 0;
>
>> + }
>> +
>> lock_sock(sk);
>> if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
>> ret = -EBUSY;
>> } else {
>> - po->has_vnet_hdr = !!val;
>> + po->vnet_hdr_sz = hdr_len;
>> ret = 0;
>> }
>> release_sock(sk);
>> @@ -4068,7 +4095,10 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
>> val = po->origdev;
>> break;
>> case PACKET_VNET_HDR:
>> - val = po->has_vnet_hdr;
>> + val = !!po->vnet_hdr_sz;
>> + break;
>> + case PACKET_VNET_HDR_SZ:
>> + val = po->vnet_hdr_sz;
>> break;
>> case PACKET_VERSION:
>> val = po->tp_version;
>> diff --git a/net/packet/diag.c b/net/packet/diag.c
>> index 07812ae..4e544da 100644
>> --- a/net/packet/diag.c
>> +++ b/net/packet/diag.c
>> @@ -27,7 +27,7 @@ static int pdiag_put_info(const struct packet_sock *po, struct sk_buff *nlskb)
>> pinfo.pdi_flags |= PDI_AUXDATA;
>> if (po->origdev)
>> pinfo.pdi_flags |= PDI_ORIGDEV;
>> - if (po->has_vnet_hdr)
>> + if (po->vnet_hdr_sz != 0)
>> pinfo.pdi_flags |= PDI_VNETHDR;
>> if (po->tp_loss)
>> pinfo.pdi_flags |= PDI_LOSS;
>> diff --git a/net/packet/internal.h b/net/packet/internal.h
>> index 48af35b..9b52d93 100644
>> --- a/net/packet/internal.h
>> +++ b/net/packet/internal.h
>> @@ -119,9 +119,9 @@ struct packet_sock {
>> unsigned int running; /* bind_lock must be held */
>> unsigned int auxdata:1, /* writer must hold sock lock */
>> origdev:1,
>> - has_vnet_hdr:1,
>> tp_loss:1,
>> - tp_tx_has_off:1;
>> + tp_tx_has_off:1,
>> + vnet_hdr_sz:8;
> just a separate u8 variable , rather than 8 bits in a u32.
>
>> int pressure;
>> int ifindex; /* bound device */
We plan to add
+ u8 vnet_hdr_sz:8;
here.
Is this a proper place to add this field to make sure the cacheline will not be broken?
>> __be16 num;
>> --
>> 1.8.3.1
>>
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