From: Stanislav Kinsburskiy <skinsbur...@virtuozzo.com> Patchset description:
netlink: prepare to dump and restore data from a receive queue CRIU can dump queued data for unix and tcp sockets, now it's time for netlink sockets. Here are there questions. * How to dump data from a receive queue We can set peeking offset like we do for unix sockets. * How to restore data back to a receive queue I suggest to add a repair mode like we do for tcp sockets. * When we can dump data from a receive queue. I think we can do this only if a socket doesn't have a running callback. Andrey Vagin (3): netlink: allow to set peeking offset for sockets netlink: add an ability to restore messages in a receive queue netlink/diag: report flags for netlink sockets https://jira.sw.ru/browse/PSBM-28386 khorenko@: there is no locking right now, but while we are the only user for this interface, this is not essential at the moment, we'll add locking on top later in the scope of: https://jira.sw.ru/browse/PSBM-48484 =========================================================== This patch description: This allows us to read socket's queue without removing skbs from it. The same logic was implemented for unix and inet sockets and we use this to dump and restore sockets in CRIU. Here is a question whether sk_peek_off has to be protected by locks. Currently it isn't protected and an user who uses sk_peek_off has to be sure that nobody calls recvmsg for a socket except him. https://jira.sw.ru/browse/PSBM-28386 Signed-off-by: Andrey Vagin <ava...@virtuozzo.com> Reviewed-by: Cyrill Gorcunov <gorcu...@virtuozzo.com> =========================================================== netlink: Don't manipulate @sk_peek_off if data fetching failed When skb_copy_datagram_iovec called to fetch queued data it may fail with EFAULT and if MSG_PEEK set by a caller the position get advanced even if data hasn't been read. So we might loose data bits here on subsequent recvmsg calls. Instead lets exit early with error. In sake of https://jira.sw.ru/browse/PSBM-57921 Signed-off-by: Cyrill Gorcunov <gorcu...@openvz.org> Acked-by: Andrey Vagin <ava...@virtuozzo.com> https://jira.sw.ru/browse/PSBM-101289 vz7 commit: 081614621eb6e ("netlink: allow to set peeking offset for sockets") Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com> Signed-off-by: Cyrill Gorcunov <gorcu...@virtuozzo.com> --- net/netlink/af_netlink.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 454110ce2a6c..6042bbc8c560 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1959,17 +1959,19 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, struct scm_cookie scm; struct sock *sk = sock->sk; struct netlink_sock *nlk = nlk_sk(sk); - int noblock = flags & MSG_DONTWAIT; size_t copied; struct sk_buff *skb, *data_skb; + int skip; int err, ret; if (flags & MSG_OOB) return -EOPNOTSUPP; copied = 0; + skip = sk_peek_offset(sk, flags); - skb = skb_recv_datagram(sk, flags, noblock, &err); + skb = __skb_recv_datagram(sk, &sk->sk_receive_queue, flags, + &skip, &err); if (skb == NULL) goto out; @@ -1997,14 +1999,20 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len, SKB_WITH_OVERHEAD(32768)); - copied = data_skb->len; + copied = data_skb->len - skip; if (len < copied) { msg->msg_flags |= MSG_TRUNC; copied = len; } skb_reset_transport_header(data_skb); - err = skb_copy_datagram_msg(data_skb, 0, msg, copied); + err = skb_copy_datagram_msg(data_skb, skip, msg, copied); + if (!err) { + if (flags & MSG_PEEK) + sk_peek_offset_fwd(sk, copied); + else + sk_peek_offset_bwd(sk, skb->len); + } if (msg->msg_name) { DECLARE_SOCKADDR(struct sockaddr_nl *, addr, msg->msg_name); @@ -2023,7 +2031,7 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, memset(&scm, 0, sizeof(scm)); scm.creds = *NETLINK_CREDS(skb); if (flags & MSG_TRUNC) - copied = data_skb->len; + copied = data_skb->len - skip; skb_free_datagram(sk, skb); @@ -2771,6 +2779,13 @@ int netlink_unregister_notifier(struct notifier_block *nb) } EXPORT_SYMBOL(netlink_unregister_notifier); +static int netlink_set_peek_off(struct sock *sk, int val) +{ + sk->sk_peek_off = val; + + return 0; +} + static const struct proto_ops netlink_ops = { .family = PF_NETLINK, .owner = THIS_MODULE, @@ -2790,6 +2805,7 @@ static const struct proto_ops netlink_ops = { .recvmsg = netlink_recvmsg, .mmap = sock_no_mmap, .sendpage = sock_no_sendpage, + .set_peek_off = netlink_set_peek_off, }; static const struct net_proto_family netlink_family_ops = { -- 2.31.1 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel