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    Subject[PATCH 5.15 075/201] net: skb: use kfree_skb_reason() in tcp_v4_rcv()
    Date
    From: Menglong Dong <imagedong@tencent.com>

    [ Upstream commit 85125597419aec3aa7b8f3b8713e415f997796f2 ]

    Replace kfree_skb() with kfree_skb_reason() in tcp_v4_rcv(). Following
    drop reasons are added:

    SKB_DROP_REASON_NO_SOCKET
    SKB_DROP_REASON_PKT_TOO_SMALL
    SKB_DROP_REASON_TCP_CSUM
    SKB_DROP_REASON_TCP_FILTER

    After this patch, 'kfree_skb' event will print message like this:

    $ TASK-PID CPU# ||||| TIMESTAMP FUNCTION
    $ | | | ||||| | |
    <idle>-0 [000] ..s1. 36.113438: kfree_skb: skbaddr=(____ptrval____) protocol=2048 location=(____ptrval____) reason: NO_SOCKET

    The reason of skb drop is printed too.

    Signed-off-by: Menglong Dong <imagedong@tencent.com>
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/linux/skbuff.h | 4 ++++
    include/trace/events/skb.h | 4 ++++
    net/ipv4/tcp_ipv4.c | 14 +++++++++++---
    3 files changed, 19 insertions(+), 3 deletions(-)

    diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
    index 029bc228bcf9..5305af6cc86f 100644
    --- a/include/linux/skbuff.h
    +++ b/include/linux/skbuff.h
    @@ -312,6 +312,10 @@ struct sk_buff;
    */
    enum skb_drop_reason {
    SKB_DROP_REASON_NOT_SPECIFIED,
    + SKB_DROP_REASON_NO_SOCKET,
    + SKB_DROP_REASON_PKT_TOO_SMALL,
    + SKB_DROP_REASON_TCP_CSUM,
    + SKB_DROP_REASON_TCP_FILTER,
    SKB_DROP_REASON_MAX,
    };

    diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
    index 294c61bbe44b..faa7d068a7bc 100644
    --- a/include/trace/events/skb.h
    +++ b/include/trace/events/skb.h
    @@ -11,6 +11,10 @@

    #define TRACE_SKB_DROP_REASON \
    EM(SKB_DROP_REASON_NOT_SPECIFIED, NOT_SPECIFIED) \
    + EM(SKB_DROP_REASON_NO_SOCKET, NO_SOCKET) \
    + EM(SKB_DROP_REASON_PKT_TOO_SMALL, PKT_TOO_SMALL) \
    + EM(SKB_DROP_REASON_TCP_CSUM, TCP_CSUM) \
    + EM(SKB_DROP_REASON_TCP_FILTER, TCP_FILTER) \
    EMe(SKB_DROP_REASON_MAX, MAX)

    #undef EM
    diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
    index b9a9f288bfa6..d901858aa440 100644
    --- a/net/ipv4/tcp_ipv4.c
    +++ b/net/ipv4/tcp_ipv4.c
    @@ -1976,8 +1976,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
    const struct tcphdr *th;
    bool refcounted;
    struct sock *sk;
    + int drop_reason;
    int ret;

    + drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
    if (skb->pkt_type != PACKET_HOST)
    goto discard_it;

    @@ -1989,8 +1991,10 @@ int tcp_v4_rcv(struct sk_buff *skb)

    th = (const struct tcphdr *)skb->data;

    - if (unlikely(th->doff < sizeof(struct tcphdr) / 4))
    + if (unlikely(th->doff < sizeof(struct tcphdr) / 4)) {
    + drop_reason = SKB_DROP_REASON_PKT_TOO_SMALL;
    goto bad_packet;
    + }
    if (!pskb_may_pull(skb, th->doff * 4))
    goto discard_it;

    @@ -2093,8 +2097,10 @@ int tcp_v4_rcv(struct sk_buff *skb)

    nf_reset_ct(skb);

    - if (tcp_filter(sk, skb))
    + if (tcp_filter(sk, skb)) {
    + drop_reason = SKB_DROP_REASON_TCP_FILTER;
    goto discard_and_relse;
    + }
    th = (const struct tcphdr *)skb->data;
    iph = ip_hdr(skb);
    tcp_v4_fill_cb(skb, iph, th);
    @@ -2131,6 +2137,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
    return ret;

    no_tcp_socket:
    + drop_reason = SKB_DROP_REASON_NO_SOCKET;
    if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
    goto discard_it;

    @@ -2138,6 +2145,7 @@ int tcp_v4_rcv(struct sk_buff *skb)

    if (tcp_checksum_complete(skb)) {
    csum_error:
    + drop_reason = SKB_DROP_REASON_TCP_CSUM;
    trace_tcp_bad_csum(skb);
    __TCP_INC_STATS(net, TCP_MIB_CSUMERRORS);
    bad_packet:
    @@ -2148,7 +2156,7 @@ int tcp_v4_rcv(struct sk_buff *skb)

    discard_it:
    /* Discard frame. */
    - kfree_skb(skb);
    + kfree_skb_reason(skb, drop_reason);
    return 0;

    discard_and_relse:
    --
    2.35.1


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