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Message-ID: <664f5938d2bef_1b5d2429467@willemb.c.googlers.com.notmuch>
Date: Thu, 23 May 2024 10:56:56 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Chengen Du <chengen.du@...onical.com>,
willemdebruijn.kernel@...il.com
Cc: davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
Chengen Du <chengen.du@...onical.com>
Subject: Re: [PATCH] af_packet: Handle outgoing VLAN packets without hardware
offloading
Chengen Du wrote:
> In the outbound packet path, if hardware VLAN offloading is unavailable,
> the VLAN tag is inserted into the payload but then cleared from the
> metadata. Consequently, this could lead to a false negative result when
> checking for the presence of a VLAN tag using skb_vlan_tag_present(),
> causing the packet sniffing outcome to lack VLAN tag information. As a
> result, the packet capturing tool may be unable to parse packets as
> expected.
>
> Signed-off-by: Chengen Du <chengen.du@...onical.com>
Fixes tag and Cc: stable.
As discussed please add more detail to the commit message that
explains the bug. And/or add a Link: for instance to the github
issue.
> ---
> net/packet/af_packet.c | 25 +++++++++++++++++++------
> 1 file changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index ea3ebc160e25..73e9acb1875b 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -1010,12 +1010,15 @@ static void prb_fill_vlan_info(struct tpacket_kbdq_core *pkc,
> if (skb_vlan_tag_present(pkc->skb)) {
> ppd->hv1.tp_vlan_tci = skb_vlan_tag_get(pkc->skb);
> ppd->hv1.tp_vlan_tpid = ntohs(pkc->skb->vlan_proto);
> - ppd->tp_status = TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
> + } else if (eth_type_vlan(pkc->skb->protocol)) {
> + ppd->hv1.tp_vlan_tci = ntohs(vlan_eth_hdr(pkc->skb)->h_vlan_TCI);
> + ppd->hv1.tp_vlan_tpid = ntohs(pkc->skb->protocol);
> } else {
> ppd->hv1.tp_vlan_tci = 0;
> ppd->hv1.tp_vlan_tpid = 0;
> - ppd->tp_status = TP_STATUS_AVAILABLE;
> }
> + ppd->tp_status = (ppd->hv1.tp_vlan_tci || ppd->hv1.tp_vlan_tpid) ?
> + TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID : TP_STATUS_AVAILABLE;
Don't move this out of the original branch and don't make the valid
conditional on the value of tp_vlan_tci. Just duplicating the line
to both branches is fine. Here and below.
> }
>
> static void prb_run_all_ft_ops(struct tpacket_kbdq_core *pkc,
> @@ -2427,11 +2430,15 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
> if (skb_vlan_tag_present(skb)) {
> h.h2->tp_vlan_tci = skb_vlan_tag_get(skb);
> h.h2->tp_vlan_tpid = ntohs(skb->vlan_proto);
> - status |= TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
> + } else if (eth_type_vlan(skb->protocol)) {
> + h.h2->tp_vlan_tci = ntohs(vlan_eth_hdr(skb)->h_vlan_TCI);
> + h.h2->tp_vlan_tpid = ntohs(skb->protocol);
> } else {
> h.h2->tp_vlan_tci = 0;
> h.h2->tp_vlan_tpid = 0;
> }
> + if (h.h2->tp_vlan_tci || h.h2->tp_vlan_tpid)
> + status |= TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
> memset(h.h2->tp_padding, 0, sizeof(h.h2->tp_padding));
> hdrlen = sizeof(*h.h2);
> break;
> @@ -2457,7 +2464,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
> sll->sll_halen = dev_parse_header(skb, sll->sll_addr);
> sll->sll_family = AF_PACKET;
> sll->sll_hatype = dev->type;
> - sll->sll_protocol = skb->protocol;
> + sll->sll_protocol = eth_type_vlan(skb->protocol) ?
> + vlan_eth_hdr(skb)->h_vlan_encapsulated_proto : skb->protocol;
For QinQ you probably want the true network protocol, not the inner
VLAN tag.
> sll->sll_pkttype = skb->pkt_type;
> if (unlikely(packet_sock_flag(po, PACKET_SOCK_ORIGDEV)))
> sll->sll_ifindex = orig_dev->ifindex;
> @@ -3482,7 +3490,8 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> /* Original length was stored in sockaddr_ll fields */
> origlen = PACKET_SKB_CB(skb)->sa.origlen;
> sll->sll_family = AF_PACKET;
> - sll->sll_protocol = skb->protocol;
> + sll->sll_protocol = eth_type_vlan(skb->protocol) ?
> + vlan_eth_hdr(skb)->h_vlan_encapsulated_proto : skb->protocol;
> }
>
> sock_recv_cmsgs(msg, sk, skb);
> @@ -3538,11 +3547,15 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> if (skb_vlan_tag_present(skb)) {
> aux.tp_vlan_tci = skb_vlan_tag_get(skb);
> aux.tp_vlan_tpid = ntohs(skb->vlan_proto);
> - aux.tp_status |= TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
> + } else if (eth_type_vlan(skb->protocol)) {
> + aux.tp_vlan_tci = ntohs(vlan_eth_hdr(skb)->h_vlan_TCI);
> + aux.tp_vlan_tpid = ntohs(skb->protocol);
> } else {
> aux.tp_vlan_tci = 0;
> aux.tp_vlan_tpid = 0;
> }
> + if (aux.tp_vlan_tci || aux.tp_vlan_tpid)
> + aux.tp_status |= TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
> put_cmsg(msg, SOL_PACKET, PACKET_AUXDATA, sizeof(aux), &aux);
> }
>
> --
> 2.40.1
>
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