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Message-Id: <20190110142529.14315-1-dh.herrmann@gmail.com>
Date: Thu, 10 Jan 2019 15:25:27 +0100
From: David Herrmann <dh.herrmann@...il.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, teg@...m.no,
David Herrmann <dh.herrmann@...il.com>
Subject: [PATCH 1/3] net: introduce SO_BINDTOIF sockopt
This introduces a new generic SOL_SOCKET-level socket option called
SO_BINDTOIF. It behaves similar to SO_BINDTODEVICE, but takes a network
interface index as argument, rather than the network interface name.
User-space often refers to network-interfaces via their index, but has
to temporarily resolve it to a name for a call into SO_BINDTODEVICE.
This might pose problems when the network-device is renamed
asynchronously by other parts of the system. When this happens, the
SO_BINDTODEVICE might either fail, or worse, it might bind to the wrong
device.
In most cases user-space only ever operates on devices which they
either manage themselves, or otherwise have a guarantee that the device
name will not change (e.g., devices that are UP cannot be renamed).
However, particularly in libraries this guarantee is non-obvious and it
would be nice if that race-condition would simply not exist. It would
make it easier for those libraries to operate even in situations where
the device-name might change under the hood.
A real use-case that we recently hit is trying to start the network
stack early in the initrd but make it survive into the real system.
Existing distributions rename network-interfaces during the transition
from initrd into the real system. This, obviously, cannot affect
devices that are up and running (unless you also consider moving them
between network-namespaces). However, the network manager now has to
make sure its management engine for dormant devices will not run in
parallel to these renames. Particularly, when you offload operations
like DHCP into separate processes, these might setup their sockets
early, and thus have to resolve the device-name possibly running into
this race-condition.
By avoiding a call to resolve the device-name, we no longer depend on
the name and can run network setup of dormant devices in parallel to
the transition off the initrd. The SO_BINDTOIF ioctl plugs this race.
Signed-off-by: David Herrmann <dh.herrmann@...il.com>
---
arch/alpha/include/uapi/asm/socket.h | 2 ++
arch/ia64/include/uapi/asm/socket.h | 2 ++
arch/mips/include/uapi/asm/socket.h | 2 ++
arch/parisc/include/uapi/asm/socket.h | 2 ++
arch/s390/include/uapi/asm/socket.h | 2 ++
arch/sparc/include/uapi/asm/socket.h | 2 ++
arch/xtensa/include/uapi/asm/socket.h | 2 ++
include/uapi/asm-generic/socket.h | 2 ++
net/core/sock.c | 46 +++++++++++++++++++++------
9 files changed, 52 insertions(+), 10 deletions(-)
diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index 065fb372e355..6e346e51eec7 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -115,4 +115,6 @@
#define SO_TXTIME 61
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 62
+
#endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/ia64/include/uapi/asm/socket.h b/arch/ia64/include/uapi/asm/socket.h
index c872c4e6bafb..ece83ba17b9d 100644
--- a/arch/ia64/include/uapi/asm/socket.h
+++ b/arch/ia64/include/uapi/asm/socket.h
@@ -117,4 +117,6 @@
#define SO_TXTIME 61
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 62
+
#endif /* _ASM_IA64_SOCKET_H */
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index 71370fb3ceef..27f7f761ace5 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -126,4 +126,6 @@
#define SO_TXTIME 61
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 62
+
#endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
index 061b9cf2a779..efd3917f23e1 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -107,4 +107,6 @@
#define SO_TXTIME 0x4036
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 0x4037
+
#endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/s390/include/uapi/asm/socket.h b/arch/s390/include/uapi/asm/socket.h
index 39d901476ee5..c8ba542e69e6 100644
--- a/arch/s390/include/uapi/asm/socket.h
+++ b/arch/s390/include/uapi/asm/socket.h
@@ -114,4 +114,6 @@
#define SO_TXTIME 61
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 62
+
#endif /* _ASM_SOCKET_H */
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index 7ea35e5601b6..50006bde7dc0 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -104,6 +104,8 @@
#define SO_TXTIME 0x003f
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 0x0040
+
/* Security levels - as per NRL IPv6 - don't actually do anything */
#define SO_SECURITY_AUTHENTICATION 0x5001
#define SO_SECURITY_ENCRYPTION_TRANSPORT 0x5002
diff --git a/arch/xtensa/include/uapi/asm/socket.h b/arch/xtensa/include/uapi/asm/socket.h
index 1de07a7f7680..a36241ffbd86 100644
--- a/arch/xtensa/include/uapi/asm/socket.h
+++ b/arch/xtensa/include/uapi/asm/socket.h
@@ -119,4 +119,6 @@
#define SO_TXTIME 61
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 62
+
#endif /* _XTENSA_SOCKET_H */
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index a12692e5f7a8..31fb8414ea4c 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -110,4 +110,6 @@
#define SO_TXTIME 61
#define SCM_TXTIME SO_TXTIME
+#define SO_BINDTOIF 62
+
#endif /* __ASM_GENERIC_SOCKET_H */
diff --git a/net/core/sock.c b/net/core/sock.c
index 6aa2e7e0b4fb..df8f83bc22b3 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -520,20 +520,43 @@ struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie)
}
EXPORT_SYMBOL(sk_dst_check);
-static int sock_setbindtodevice(struct sock *sk, char __user *optval,
- int optlen)
+static int sock_setbindtodevice_locked(struct sock *sk, int ifindex)
{
int ret = -ENOPROTOOPT;
#ifdef CONFIG_NETDEVICES
struct net *net = sock_net(sk);
- char devname[IFNAMSIZ];
- int index;
/* Sorry... */
ret = -EPERM;
if (!ns_capable(net->user_ns, CAP_NET_RAW))
goto out;
+ ret = -EINVAL;
+ if (ifindex < 0)
+ goto out;
+
+ sk->sk_bound_dev_if = ifindex;
+ if (sk->sk_prot->rehash)
+ sk->sk_prot->rehash(sk);
+ sk_dst_reset(sk);
+
+ ret = 0;
+
+out:
+#endif
+
+ return ret;
+}
+
+static int sock_setbindtodevice(struct sock *sk, char __user *optval,
+ int optlen)
+{
+ int ret = -ENOPROTOOPT;
+#ifdef CONFIG_NETDEVICES
+ struct net *net = sock_net(sk);
+ char devname[IFNAMSIZ];
+ int index;
+
ret = -EINVAL;
if (optlen < 0)
goto out;
@@ -566,14 +589,9 @@ static int sock_setbindtodevice(struct sock *sk, char __user *optval,
}
lock_sock(sk);
- sk->sk_bound_dev_if = index;
- if (sk->sk_prot->rehash)
- sk->sk_prot->rehash(sk);
- sk_dst_reset(sk);
+ ret = sock_setbindtodevice_locked(sk, index);
release_sock(sk);
- ret = 0;
-
out:
#endif
@@ -1055,6 +1073,10 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
}
break;
+ case SO_BINDTOIF:
+ ret = sock_setbindtodevice_locked(sk, val);
+ break;
+
default:
ret = -ENOPROTOOPT;
break;
@@ -1399,6 +1421,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
SOF_TXTIME_REPORT_ERRORS : 0;
break;
+ case SO_BINDTOIF:
+ v.val = sk->sk_bound_dev_if;
+ break;
+
default:
/* We implement the SO_SNDLOWAT etc to not be settable
* (1003.1g 7).
--
2.20.1
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