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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-434d52cad51sm92807595e9.36.2024.12.06.05.35.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Dec 2024 05:35:36 -0800 (PST) Date: Fri, 6 Dec 2024 14:35:35 +0100 From: Stefano Brivio To: Paolo Abeni Cc: Willem de Bruijn , Eric Dumazet , netdev@vger.kernel.org, Kuniyuki Iwashima , Mike Manning , David Gibson , Paul Holzinger , Philo Lu , Cambda Zhu , Fred Chen , Yubing Qiu Subject: Re: [PATCH net-next 2/2] datagram, udp: Set local address and rehash socket atomically against lookup Message-ID: <20241206143535.3e095320@elisabeth> In-Reply-To: References: <20241204221254.3537932-1-sbrivio@redhat.com> <20241204221254.3537932-3-sbrivio@redhat.com> <20241205165830.64da6fd7@elisabeth> <20241206115042.4e98ff8b@elisabeth> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 6 Dec 2024 13:36:47 +0100 Paolo Abeni wrote: > On 12/6/24 11:50, Stefano Brivio wrote: > > On Thu, 5 Dec 2024 17:53:33 +0100 Paolo Abeni wrote: > >> I'm wondering if the issue could be solved (almost) entirely in the > >> rehash callback?!? if the rehash happens on connect and the the socket > >> does not have hash4 yet (it's not a reconnect) do the l4 hashing before > >> everything else. > > > > So, yes, that's actually the first thing I tried: do the hashing (any > > hash) before setting the address (I guess that's what you mean by > > "everything else"). > > > > If you take this series, and drop the changes in __udp4_lib_lookup(), I > > guess that would match what you suggest. > > I mean something slightly different. Just to explain the idea something > alike the following (completely untested): > > --- > diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c > index cc6d0bd7b0a9..e9cc6edbcdc6 100644 > --- a/net/ipv4/datagram.c > +++ b/net/ipv4/datagram.c > @@ -61,6 +61,10 @@ int __ip4_datagram_connect(struct sock *sk, struct > sockaddr *uaddr, int addr_len > err = -EACCES; > goto out; > } > + > + sk->sk_state = TCP_ESTABLISHED; > + inet->inet_daddr = fl4->daddr; > + inet->inet_dport = usin->sin_port; > if (!inet->inet_saddr) > inet->inet_saddr = fl4->saddr; /* Update source address */ > if (!inet->inet_rcv_saddr) { > @@ -68,10 +72,7 @@ int __ip4_datagram_connect(struct sock *sk, struct > sockaddr *uaddr, int addr_len > if (sk->sk_prot->rehash) > sk->sk_prot->rehash(sk); > } > - inet->inet_daddr = fl4->daddr; > - inet->inet_dport = usin->sin_port; > reuseport_has_conns_set(sk); > - sk->sk_state = TCP_ESTABLISHED; > sk_set_txhash(sk); > atomic_set(&inet->inet_id, get_random_u16()); > > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > index 6a01905d379f..c6c58b0a6b7b 100644 > --- a/net/ipv4/udp.c > +++ b/net/ipv4/udp.c > @@ -2194,6 +2194,21 @@ void udp_lib_rehash(struct sock *sk, u16 newhash, > u16 newhash4) > if (rcu_access_pointer(sk->sk_reuseport_cb)) > reuseport_detach_sock(sk); > > + if (sk->sk_state == TCP_ESTABLISHED && !udp_hashed4(sk)) { > + struct udp_hslot * hslot4 = udp_hashslot4(udptable, newhash4); > + > + udp_sk(sk)->udp_lrpa_hash = newhash4; > + spin_lock(&hslot4->lock); > + hlist_nulls_add_head_rcu(&udp_sk(sk)->udp_lrpa_node, > + &hslot4->nulls_head); > + hslot4->count++; > + spin_unlock(&hslot4->lock); > + > + spin_lock(&hslot2->lock); > + udp_hash4_inc(hslot2); > + spin_unlock(&hslot2->lock); > + } > + > if (hslot2 != nhslot2) { > spin_lock(&hslot2->lock); > hlist_del_init_rcu(&udp_sk(sk)->udp_portaddr_node); > --- > > Basically the idea is to leverage the hash4 - which should be not yet > initialized when rehash is invoked due to connect(). That assumption seems to be correct from my tests. > In such a case, before touching hash{,2}, do hash4. Brilliant, thanks. I'll give that a try. -- Stefano