Re: [PATCH RESEND net-next] tcp: socket-specific version of WARN_ON_ONCE()
From: Eric Dumazet <edumazet@google.com>
Date: 2022-09-03 16:43:00
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On Wed, Aug 31, 2022 at 6:38 AM Breno Leitao [off-list ref] wrote:
There are cases where we need information about the socket during a warning, so, it could help us to find bugs that happens that do not have a easily repro. BPF congestion control algorithms can change socket state in unexpected ways, leading to WARNings. Additional information about the socket state is useful to identify the culprit.
Well, this suggests we need to fix BPF side ?
Not sure how this can happen, because TCP_BPF_IW has
if (val <= 0 || tp->data_segs_out > tp->syn_data)
ret = -EINVAL;
else
tcp_snd_cwnd_set(tp, val);
It seems you already found the issue in an eBPF CC, can you share the details ?
This diff creates a TCP socket-specific version of WARN_ON_ONCE(), and attaches it to tcp_snd_cwnd_set().
Well, I feel this will need constant additions... the state of a custom BPF CC is opaque to core TCP stack anyway ?
quoted hunk ↗ jump to hunk
Signed-off-by: Breno Leitao <leitao@debian.org> --- include/net/tcp.h | 3 ++- include/net/tcp_debug.h | 10 ++++++++++ net/ipv4/tcp.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 42 insertions(+), 1 deletion(-) create mode 100644 include/net/tcp_debug.hdiff --git a/include/net/tcp.h b/include/net/tcp.h index d10962b9f0d0..73c3970d8839 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h@@ -40,6 +40,7 @@ #include <net/inet_ecn.h> #include <net/dst.h> #include <net/mptcp.h> +#include <net/tcp_debug.h> #include <linux/seq_file.h> #include <linux/memcontrol.h>@@ -1222,7 +1223,7 @@ static inline u32 tcp_snd_cwnd(const struct tcp_sock *tp) static inline void tcp_snd_cwnd_set(struct tcp_sock *tp, u32 val) { - WARN_ON_ONCE((int)val <= 0); + TCP_SOCK_WARN_ON_ONCE(tp, (int)val <= 0); tp->snd_cwnd = val; }diff --git a/include/net/tcp_debug.h b/include/net/tcp_debug.h new file mode 100644 index 000000000000..50e96d87d335 --- /dev/null +++ b/include/net/tcp_debug.h@@ -0,0 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_TCP_DEBUG_H +#define _LINUX_TCP_DEBUG_H + +void tcp_sock_warn(const struct tcp_sock *tp); + +#define TCP_SOCK_WARN_ON_ONCE(tcp_sock, condition) \ + DO_ONCE_LITE_IF(condition, tcp_sock_warn, tcp_sock) + +#endif /* _LINUX_TCP_DEBUG_H */diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index bbe218753662..71771fee72f7 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c@@ -4684,6 +4684,36 @@ int tcp_abort(struct sock *sk, int err) } EXPORT_SYMBOL_GPL(tcp_abort); +void tcp_sock_warn(const struct tcp_sock *tp) +{ + const struct sock *sk = (const struct sock *)tp; + struct inet_sock *inet = inet_sk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + + WARN_ON(1); + + if (!tp) + return; + + pr_warn("Socket Info: family=%u state=%d sport=%u dport=%u ccname=%s cwnd=%u", + sk->sk_family, sk->sk_state, ntohs(inet->inet_sport), + ntohs(inet->inet_dport), icsk->icsk_ca_ops->name, tcp_snd_cwnd(tp)); + + switch (sk->sk_family) { + case AF_INET: + pr_warn("saddr=%pI4 daddr=%pI4", &inet->inet_saddr, + &inet->inet_daddr); + break; +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: + pr_warn("saddr=%pI6 daddr=%pI6", &sk->sk_v6_rcv_saddr, + &sk->sk_v6_daddr); + break; +#endif + } +} +EXPORT_SYMBOL_GPL(tcp_sock_warn); + extern struct tcp_congestion_ops tcp_reno; static __initdata unsigned long thash_entries; --2.30.2