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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id o40sm11085293pjb.18.2020.04.14.11.44.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Apr 2020 11:44:01 -0700 (PDT) Subject: Re: [PATCH v3] net: UDP repair mode for retrieving the send queue of corked UDP socket To: =?UTF-8?B?TGXFn2UgRG9ydSBDxINsaW4=?= , Leon Romanovsky , netdev@vger.kernel.org Cc: David Miller , Alexey Kuznetsov , Hideaki YOSHIFUJI References: <20200414090925.GA10402@white> From: Eric Dumazet Message-ID: Date: Tue, 14 Apr 2020 11:43:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200414090925.GA10402@white> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/14/20 2:09 AM, Leşe Doru Călin wrote: > In this year's edition of GSoC, there is a project idea for CRIU to add > support for checkpoint/restore of cork-ed UDP sockets. But to add it, the > kernel API needs to be extended. > > This is what this patch does. It adds UDP "repair mode" for UDP sockets in > a similar approach to the TCP "repair mode", but only the send queue is > necessary to be retrieved. So the patch extends the recv and setsockopt > syscalls. Using UDP_REPAIR option in setsockopt, caller can set the socket > in repair mode. If it is setted, the recv/recvfrom/recvmsg will receive the > write queue and the destination of the data. As in the TCP mode, to change > the repair mode requires the CAP_NET_ADMIN capability and to receive data > the caller is obliged to use the MSG_PEEK flag. > > Signed-off-by: Lese Doru Calin > --- > include/linux/udp.h | 3 ++- > include/uapi/linux/udp.h | 1 + > net/ipv4/udp.c | 55 ++++++++++++++++++++++++++++++++++++++++ > net/ipv6/udp.c | 45 ++++++++++++++++++++++++++++++++ > 4 files changed, 103 insertions(+), 1 deletion(-) > > diff --git a/include/linux/udp.h b/include/linux/udp.h > index aa84597bdc33..b22bd70118ce 100644 > --- a/include/linux/udp.h > +++ b/include/linux/udp.h > @@ -51,7 +51,8 @@ struct udp_sock { > * different encapsulation layer set > * this > */ > - gro_enabled:1; /* Can accept GRO packets */ > + gro_enabled:1, /* Can accept GRO packets */ > + repair:1;/* Receive the send queue */ > /* > * Following member retains the information to create a UDP header > * when the socket is uncorked. > diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h > index 4828794efcf8..2fe78329d6da 100644 > --- a/include/uapi/linux/udp.h > +++ b/include/uapi/linux/udp.h > @@ -29,6 +29,7 @@ struct udphdr { > > /* UDP socket options */ > #define UDP_CORK 1 /* Never send partially complete segments */ > +#define UDP_REPAIR 19 /* Receive the send queue */ > #define UDP_ENCAP 100 /* Set the socket to accept encapsulated packets */ > #define UDP_NO_CHECK6_TX 101 /* Disable sending checksum for UDP6X */ > #define UDP_NO_CHECK6_RX 102 /* Disable accpeting checksum for UDP6 */ > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > index 32564b350823..dc9d15d564d6 100644 > --- a/net/ipv4/udp.c > +++ b/net/ipv4/udp.c > @@ -1720,6 +1720,28 @@ struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags, > } > EXPORT_SYMBOL(__skb_recv_udp); > > +static int udp_peek_sndq(struct sock *sk, struct msghdr *msg, int off, int len) > +{ > + int copy, copied = 0, err = 0; > + struct sk_buff *skb; > + > + skb_queue_walk(&sk->sk_write_queue, skb) { > + copy = len - copied; > + if (copy > skb->len - off) > + copy = skb->len - off; > + > + err = skb_copy_datagram_msg(skb, off, msg, copy); > + if (err) > + break; > + > + copied += copy; > + > + if (len <= copied) > + break; > + } > + return err ?: copied; > +} > + > /* > * This should be easy, if there is something there we > * return it, otherwise we block. > @@ -1729,8 +1751,10 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock, > int flags, int *addr_len) > { > struct inet_sock *inet = inet_sk(sk); > + struct udp_sock *up = udp_sk(sk); > DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name); > struct sk_buff *skb; > + struct flowi4 *fl4; > unsigned int ulen, copied; > int off, err, peeking = flags & MSG_PEEK; > int is_udplite = IS_UDPLITE(sk); > @@ -1739,6 +1763,12 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock, > if (flags & MSG_ERRQUEUE) > return ip_recv_error(sk, msg, len, addr_len); > > + if (unlikely(up->repair)) { Socket lock is not held, disaster seems possible :/ > + if (!peeking) > + return -EPERM; > + goto recv_sndq; > + } > + Really, I would rather stop adding code in fast path for REPAIR stuff. A new setsockopt() would be much better I think. > try_again: > off = sk_peek_offset(sk, flags); > skb = __skb_recv_udp(sk, flags, noblock, &off, &err); > @@ -1832,6 +1862,18 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock, > cond_resched(); > msg->msg_flags &= ~MSG_TRUNC; > goto try_again; > + > +recv_sndq: > + off = sizeof(struct iphdr) + sizeof(struct udphdr); > + if (sin) { > + fl4 = &inet->cork.fl.u.ip4; > + sin->sin_family = AF_INET; > + sin->sin_port = fl4->fl4_dport; > + sin->sin_addr.s_addr = fl4->daddr; > + memset(sin->sin_zero, 0, sizeof(sin->sin_zero)); > + *addr_len = sizeof(*sin); > + } > + return udp_peek_sndq(sk, msg, off, len); > } > > int udp_pre_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) > @@ -2557,6 +2599,15 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname, > } > break; > > + case UDP_REPAIR: > + if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) > + err = -EPERM; > + else if (val != 0) > + up->repair = 1; > + else > + up->repair = 0; > + break; > + > case UDP_ENCAP: > switch (val) { > case 0: > @@ -2678,6 +2729,10 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname, > val = up->corkflag; > break; > > + case UDP_REPAIR: > + val = up->repair; > + break; > + > case UDP_ENCAP: > val = up->encap_type; > break; > diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c > index 7d4151747340..ec653f9fce2d 100644 > --- a/net/ipv6/udp.c > +++ b/net/ipv6/udp.c > @@ -250,6 +250,28 @@ struct sock *udp6_lib_lookup(struct net *net, const struct in6_addr *saddr, __be > EXPORT_SYMBOL_GPL(udp6_lib_lookup); > #endif > > +static int udp6_peek_sndq(struct sock *sk, struct msghdr *msg, int off, int len) > +{ > + int copy, copied = 0, err = 0; > + struct sk_buff *skb; > + > + skb_queue_walk(&sk->sk_write_queue, skb) { > + copy = len - copied; > + if (copy > skb->len - off) > + copy = skb->len - off; > + > + err = skb_copy_datagram_msg(skb, off, msg, copy); > + if (err) > + break; > + > + copied += copy; > + > + if (len <= copied) > + break; > + } > + return err ?: copied; > +} > + > /* do not use the scratch area len for jumbogram: their length execeeds the > * scratch area space; note that the IP6CB flags is still in the first > * cacheline, so checking for jumbograms is cheap > @@ -269,7 +291,9 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, > { > struct ipv6_pinfo *np = inet6_sk(sk); > struct inet_sock *inet = inet_sk(sk); > + struct udp_sock *up = udp_sk(sk); > struct sk_buff *skb; > + struct flowi6 *fl6; > unsigned int ulen, copied; > int off, err, peeking = flags & MSG_PEEK; > int is_udplite = IS_UDPLITE(sk); > @@ -283,6 +307,12 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, > if (np->rxpmtu && np->rxopt.bits.rxpmtu) > return ipv6_recv_rxpmtu(sk, msg, len, addr_len); > > + if (unlikely(up->repair)) { > + if (!peeking) > + return -EPERM; > + goto recv_sndq; > + } > + > try_again: > off = sk_peek_offset(sk, flags); > skb = __skb_recv_udp(sk, flags, noblock, &off, &err); > @@ -394,6 +424,21 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, > cond_resched(); > msg->msg_flags &= ~MSG_TRUNC; > goto try_again; > + > +recv_sndq: > + off = sizeof(struct ipv6hdr) + sizeof(struct udphdr); > + if (msg->msg_name) { > + DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name); > + > + fl6 = &inet->cork.fl.u.ip6; > + sin6->sin6_family = AF_INET6; > + sin6->sin6_port = fl6->fl6_dport; > + sin6->sin6_flowinfo = 0; > + sin6->sin6_addr = fl6->daddr; > + sin6->sin6_scope_id = fl6->flowi6_oif; > + *addr_len = sizeof(*sin6); > + } > + return udp6_peek_sndq(sk, msg, off, len); > } > > DEFINE_STATIC_KEY_FALSE(udpv6_encap_needed_key); >