Userspace needs a way to identify, for example, kernels with too old an
interface, i.e. a kernel that might silently reject/ignore certain new
nlattrs.
Signed-off-by: Jan Engelhardt <jengelh@xxxxxxx>
---
include/uapi/linux/netfilter/nfnetlink_xtables.h | 4 ++++
net/netfilter/xt_nfnetlink.c | 15 +++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/include/uapi/linux/netfilter/nfnetlink_xtables.h b/include/uapi/linux/netfilter/nfnetlink_xtables.h
index 84133c7..44d6595 100644
--- a/include/uapi/linux/netfilter/nfnetlink_xtables.h
+++ b/include/uapi/linux/netfilter/nfnetlink_xtables.h
@@ -29,6 +29,8 @@ enum nfxt_msg_type {
* %NFXTA_ERRNO: system error code (%Exxx)
* %NFXTA_XTERRNO: NFXT-specific error code (cf. enum nfxt_errno)
* %NFXTA_NEW_NAME: new name of object
+ * %NFXTA_REVISION_MIN: minimum API revision supported by xtnetlink
+ * %NFXTA_REVISION_MAX: maximum API revision supported by xtnetlink
*/
enum nfxt_attr_type {
NFXTA_UNSPEC = 0,
@@ -36,6 +38,8 @@ enum nfxt_attr_type {
NFXTA_ERRNO,
NFXTA_XTERRNO,
NFXTA_NEW_NAME,
+ NFXTA_REVISION_MIN,
+ NFXTA_REVISION_MAX,
};
/**
diff --git a/net/netfilter/xt_nfnetlink.c b/net/netfilter/xt_nfnetlink.c
index c53902e..4d4a076 100644
--- a/net/netfilter/xt_nfnetlink.c
+++ b/net/netfilter/xt_nfnetlink.c
@@ -75,6 +75,13 @@ static rwlock_t xtnetlink_transact_lock;
static LIST_HEAD(xtnetlink_transact_list);
/**
+ * The revision this xt_nfnetlink speaks. Think of it like max=CURRENT and
+ * min=(CURRENT-AGE) numbers used with libtool versioning.
+ */
+static const unsigned int xtnetlink_revision_max; /* = 0; */
+static const unsigned int xtnetlink_revision_min; /* = 0; */
+
+/**
* Create a new transaction state.
* @net: network namespace of socket
* @nladdr: client address (NETLINK_CB(skb).portid)
@@ -362,6 +369,12 @@ xtnetlink_identify2(struct sk_buff *skb, struct netlink_callback *nl_cb)
return 0;
if (nla_put_string(skb, NFXTA_NAME, "Xtables2-xtnl/nfnl") != 0)
goto nla_put_failure;
+ if (nla_put_u32(skb, NFXTA_REVISION_MAX,
+ xtnetlink_revision_max) != 0)
+ goto nla_put_failure;
+ if (nla_put_u32(skb, NFXTA_REVISION_MIN,
+ xtnetlink_revision_min) != 0)
+ goto nla_put_failure;
++nl_cb->args[0];
break;
}
@@ -582,6 +595,8 @@ static const struct nla_policy xtnetlink_policy[] = {
[NFXTA_ERRNO] = {.type = NLA_U32},
[NFXTA_XTERRNO] = {.type = NLA_U32},
[NFXTA_NEW_NAME] = {.type = NLA_NUL_STRING},
+ [NFXTA_REVISION_MIN] = {.type = NLA_U32},
+ [NFXTA_REVISION_MAX] = {.type = NLA_U32},
};
/*
--
1.7.10.4
--
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