Re: [Patch bpf-next v7 4/9] skmsg: move sk_redir from TCP_SKB_CB to skb
flat view
From: Lorenz Bauer <hidden>
Date: 2021-03-01 15:25:24
Also in:
bpf
On Tue, 23 Feb 2021 at 18:49, Cong Wang [off-list ref] wrote:
From: Cong Wang <redacted> Currently TCP_SKB_CB() is hard-coded in skmsg code, it certainly does not work for any other non-TCP protocols. We can move them to skb ext, but it introduces a memory allocation on fast path. Fortunately, we only need to a word-size to store all the information, because the flags actually only contains 1 bit so can be just packed into the lowest bit of the "pointer", which is stored as unsigned long. Inside struct sk_buff, '_skb_refdst' can be reused because skb dst is no longer needed after ->sk_data_ready() so we can just drop it.
Hi Cong Wang, I saw this on patchwork: include/linux/skbuff.h:932: warning: Function parameter or member '_sk_redir' not described in 'sk_buff' New warnings added 0a1
include/linux/skbuff.h:932: warning: Function parameter or member '_sk_redir' not described in 'sk_buff'
Per-file breakdown Source: https://patchwork.kernel.org/project/netdevbpf/patch/20210223184934.6054-5-xiyou.wangcong@gmail.com/ Maybe something to follow up on, I'm not sure what the conventions are here.
quoted hunk ↗ jump to hunk
Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Lorenz Bauer <redacted> Acked-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Jakub Sitnicki <jakub@cloudflare.com> Signed-off-by: Cong Wang <redacted> --- include/linux/skbuff.h | 3 +++ include/linux/skmsg.h | 38 ++++++++++++++++++++++++++++++++++++++ include/net/tcp.h | 19 ------------------- net/core/skmsg.c | 31 +++++++++++++++++++------------ net/core/sock_map.c | 8 ++------ 5 files changed, 62 insertions(+), 37 deletions(-)diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 6d0a33d1c0db..bd84f799c952 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h@@ -755,6 +755,9 @@ struct sk_buff { void (*destructor)(struct sk_buff *skb); }; struct list_head tcp_tsorted_anchor; +#ifdef CONFIG_NET_SOCK_MSG + unsigned long _sk_redir; +#endif }; #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h index 22e26f82de33..e0de45527bb6 100644 --- a/include/linux/skmsg.h +++ b/include/linux/skmsg.h@@ -455,4 +455,42 @@ static inline bool sk_psock_strp_enabled(struct sk_psock *psock) return false; return !!psock->saved_data_ready; } + +#if IS_ENABLED(CONFIG_NET_SOCK_MSG) + +/* We only have one bit so far. */ +#define BPF_F_PTR_MASK ~(BPF_F_INGRESS) + +static inline bool skb_bpf_ingress(const struct sk_buff *skb) +{ + unsigned long sk_redir = skb->_sk_redir; + + return sk_redir & BPF_F_INGRESS; +} + +static inline void skb_bpf_set_ingress(struct sk_buff *skb) +{ + skb->_sk_redir |= BPF_F_INGRESS; +} + +static inline void skb_bpf_set_redir(struct sk_buff *skb, struct sock *sk_redir, + bool ingress) +{ + skb->_sk_redir = (unsigned long)sk_redir; + if (ingress) + skb->_sk_redir |= BPF_F_INGRESS; +} + +static inline struct sock *skb_bpf_redirect_fetch(const struct sk_buff *skb) +{ + unsigned long sk_redir = skb->_sk_redir; + + return (struct sock *)(sk_redir & BPF_F_PTR_MASK); +} + +static inline void skb_bpf_redirect_clear(struct sk_buff *skb) +{ + skb->_sk_redir = 0; +} +#endif /* CONFIG_NET_SOCK_MSG */ #endif /* _LINUX_SKMSG_H */diff --git a/include/net/tcp.h b/include/net/tcp.h index 947ef5da6867..075de26f449d 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h@@ -883,30 +883,11 @@ struct tcp_skb_cb { struct inet6_skb_parm h6; #endif } header; /* For incoming skbs */ - struct { - __u32 flags; - struct sock *sk_redir; - } bpf; }; }; #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0])) -static inline bool tcp_skb_bpf_ingress(const struct sk_buff *skb) -{ - return TCP_SKB_CB(skb)->bpf.flags & BPF_F_INGRESS; -} - -static inline struct sock *tcp_skb_bpf_redirect_fetch(struct sk_buff *skb) -{ - return TCP_SKB_CB(skb)->bpf.sk_redir; -} - -static inline void tcp_skb_bpf_redirect_clear(struct sk_buff *skb) -{ - TCP_SKB_CB(skb)->bpf.sk_redir = NULL; -} - extern const struct inet_connection_sock_af_ops ipv4_specific; #if IS_ENABLED(CONFIG_IPV6)diff --git a/net/core/skmsg.c b/net/core/skmsg.c index 8822001ab3dc..409258367bea 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c@@ -525,7 +525,8 @@ static void sk_psock_backlog(struct work_struct *work) len = skb->len; off = 0; start: - ingress = tcp_skb_bpf_ingress(skb); + ingress = skb_bpf_ingress(skb); + skb_bpf_redirect_clear(skb); do { ret = -EIO; if (likely(psock->sk->sk_socket))@@ -631,7 +632,12 @@ void __sk_psock_purge_ingress_msg(struct sk_psock *psock) static void sk_psock_zap_ingress(struct sk_psock *psock) { - __skb_queue_purge(&psock->ingress_skb); + struct sk_buff *skb; + + while ((skb = __skb_dequeue(&psock->ingress_skb)) != NULL) { + skb_bpf_redirect_clear(skb); + kfree_skb(skb); + } __sk_psock_purge_ingress_msg(psock); }@@ -754,7 +760,7 @@ static void sk_psock_skb_redirect(struct sk_buff *skb) struct sk_psock *psock_other; struct sock *sk_other; - sk_other = tcp_skb_bpf_redirect_fetch(skb); + sk_other = skb_bpf_redirect_fetch(skb); /* This error is a buggy BPF program, it returned a redirect * return code, but then didn't set a redirect interface. */@@ -804,9 +810,10 @@ int sk_psock_tls_strp_read(struct sk_psock *psock, struct sk_buff *skb) * TLS context. */ skb->sk = psock->sk; - tcp_skb_bpf_redirect_clear(skb); + skb_dst_drop(skb); + skb_bpf_redirect_clear(skb); ret = sk_psock_bpf_run(psock, prog, skb); - ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb)); + ret = sk_psock_map_verd(ret, skb_bpf_redirect_fetch(skb)); skb->sk = NULL; } sk_psock_tls_verdict_apply(skb, psock->sk, ret);@@ -818,7 +825,6 @@ EXPORT_SYMBOL_GPL(sk_psock_tls_strp_read); static void sk_psock_verdict_apply(struct sk_psock *psock, struct sk_buff *skb, int verdict) { - struct tcp_skb_cb *tcp; struct sock *sk_other; int err = -EIO;@@ -830,8 +836,7 @@ static void sk_psock_verdict_apply(struct sk_psock *psock, goto out_free; } - tcp = TCP_SKB_CB(skb); - tcp->bpf.flags |= BPF_F_INGRESS; + skb_bpf_set_ingress(skb); /* If the queue is empty then we can submit directly * into the msg queue. If its not empty we have to@@ -892,9 +897,10 @@ static void sk_psock_strp_read(struct strparser *strp, struct sk_buff *skb) skb_set_owner_r(skb, sk); prog = READ_ONCE(psock->progs.skb_verdict); if (likely(prog)) { - tcp_skb_bpf_redirect_clear(skb); + skb_dst_drop(skb); + skb_bpf_redirect_clear(skb); ret = sk_psock_bpf_run(psock, prog, skb); - ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb)); + ret = sk_psock_map_verd(ret, skb_bpf_redirect_fetch(skb)); } sk_psock_verdict_apply(psock, skb, ret); out:@@ -1011,9 +1017,10 @@ static int sk_psock_verdict_recv(read_descriptor_t *desc, struct sk_buff *skb, skb_set_owner_r(skb, sk); prog = READ_ONCE(psock->progs.skb_verdict); if (likely(prog)) { - tcp_skb_bpf_redirect_clear(skb); + skb_dst_drop(skb); + skb_bpf_redirect_clear(skb); ret = sk_psock_bpf_run(psock, prog, skb); - ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb)); + ret = sk_psock_map_verd(ret, skb_bpf_redirect_fetch(skb)); } sk_psock_verdict_apply(psock, skb, ret); out:diff --git a/net/core/sock_map.c b/net/core/sock_map.c index 1a28a5c2c61e..dbfcd7006338 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c@@ -657,7 +657,6 @@ const struct bpf_func_proto bpf_sock_map_update_proto = { BPF_CALL_4(bpf_sk_redirect_map, struct sk_buff *, skb, struct bpf_map *, map, u32, key, u64, flags) { - struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); struct sock *sk; if (unlikely(flags & ~(BPF_F_INGRESS)))@@ -667,8 +666,7 @@ BPF_CALL_4(bpf_sk_redirect_map, struct sk_buff *, skb, if (unlikely(!sk || !sock_map_redirect_allowed(sk))) return SK_DROP; - tcb->bpf.flags = flags; - tcb->bpf.sk_redir = sk; + skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS); return SK_PASS; }@@ -1250,7 +1248,6 @@ const struct bpf_func_proto bpf_sock_hash_update_proto = { BPF_CALL_4(bpf_sk_redirect_hash, struct sk_buff *, skb, struct bpf_map *, map, void *, key, u64, flags) { - struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); struct sock *sk; if (unlikely(flags & ~(BPF_F_INGRESS)))@@ -1260,8 +1257,7 @@ BPF_CALL_4(bpf_sk_redirect_hash, struct sk_buff *, skb, if (unlikely(!sk || !sock_map_redirect_allowed(sk))) return SK_DROP; - tcb->bpf.flags = flags; - tcb->bpf.sk_redir = sk; + skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS); return SK_PASS; } --2.25.1
-- Lorenz Bauer | Systems Engineer 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK www.cloudflare.com