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authorChristophe Ricard <christophe.ricard@gmail.com>2015-08-28 05:07:48 (GMT)
committerDavid S. Miller <davem@davemloft.net>2015-08-29 05:25:42 (GMT)
commit0a6a3a23ea6efde079a5b77688541a98bf202721 (patch)
treeec9cd4b088e93a12c26ebf9fcb8b7bf5abe2510d /net/netlink
parent4941b8f0c2b9d88e8a6dacebf8b7faf603b98368 (diff)
netlink: add NETLINK_CAP_ACK socket option
Since commit c05cdb1b864f ("netlink: allow large data transfers from user-space"), the kernel may fail to allocate the necessary room for the acknowledgment message back to userspace. This patch introduces a new socket option that trims off the payload of the original netlink message. The netlink message header is still included, so the user can guess from the sequence number what is the message that has triggered the acknowledgment. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/af_netlink.c27
1 files changed, 24 insertions, 3 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index a774985..3eea0b2 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -84,6 +84,7 @@ struct listeners {
#define NETLINK_F_BROADCAST_SEND_ERROR 0x4
#define NETLINK_F_RECV_NO_ENOBUFS 0x8
#define NETLINK_F_LISTEN_ALL_NSID 0x10
+#define NETLINK_F_CAP_ACK 0x20
static inline int netlink_is_kernel(struct sock *sk)
{
@@ -2258,6 +2259,13 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
nlk->flags &= ~NETLINK_F_LISTEN_ALL_NSID;
err = 0;
break;
+ case NETLINK_CAP_ACK:
+ if (val)
+ nlk->flags |= NETLINK_F_CAP_ACK;
+ else
+ nlk->flags &= ~NETLINK_F_CAP_ACK;
+ err = 0;
+ break;
default:
err = -ENOPROTOOPT;
}
@@ -2332,6 +2340,16 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
netlink_table_ungrab();
break;
}
+ case NETLINK_CAP_ACK:
+ if (len < sizeof(int))
+ return -EINVAL;
+ len = sizeof(int);
+ val = nlk->flags & NETLINK_F_CAP_ACK ? 1 : 0;
+ if (put_user(len, optlen) ||
+ put_user(val, optval))
+ return -EFAULT;
+ err = 0;
+ break;
default:
err = -ENOPROTOOPT;
}
@@ -2873,9 +2891,12 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
struct nlmsghdr *rep;
struct nlmsgerr *errmsg;
size_t payload = sizeof(*errmsg);
+ struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk);
- /* error messages get the original request appened */
- if (err)
+ /* Error messages get the original request appened, unless the user
+ * requests to cap the error message.
+ */
+ if (!(nlk->flags & NETLINK_F_CAP_ACK) && err)
payload += nlmsg_len(nlh);
skb = netlink_alloc_skb(in_skb->sk, nlmsg_total_size(payload),
@@ -2898,7 +2919,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
NLMSG_ERROR, payload, 0);
errmsg = nlmsg_data(rep);
errmsg->error = err;
- memcpy(&errmsg->msg, nlh, err ? nlh->nlmsg_len : sizeof(*nlh));
+ memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).portid, MSG_DONTWAIT);
}
EXPORT_SYMBOL(netlink_ack);

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