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Date: Tue, 14 Apr 2020 11:43:59 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: Leşe Doru Călin <lesedorucalin01@...il.com>,
Leon Romanovsky <leon@...nel.org>, netdev@...r.kernel.org
Cc: David Miller <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH v3] net: UDP repair mode for retrieving the send queue of
corked UDP socket
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 <lesedorucalin01@...il.com>
> ---
> 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);
>
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