kernel/linux.git/include/uapi/linux/netlink.h, branch v6.19.11

netlink: add variable-length / auto integers

2023-10-20T10:43:35+00:00

We currently push everyone to use padding to align 64b values in netlink. Un-padded nla_put_u64() doesn't even exist any more. The story behind this possibly start with this thread: https://lore.kernel.org/netdev/20121204.130914.1457976839967676240.davem@davemloft.net/ where DaveM was concerned about the alignment of a structure containing 64b stats. If user space tries to access such struct directly: struct some_stats *stats = nla_data(attr); printf("A: %llu", stats->a); lack of alignment may become problematic for some architectures. These days we most often put every single member in a separate attribute, meaning that the code above would use a helper like nla_get_u64(), which can deal with alignment internally. Even for arches which don't have good unaligned access - access aligned to 4B should be pretty efficient. Kernel and well known libraries deal with unaligned input already. Padded 64b is quite space-inefficient (64b + pad means at worst 16B per attr vs 32b which takes 8B). It is also more typing: if (nla_put_u64_pad(rsp, NETDEV_A_SOMETHING_SOMETHING, value, NETDEV_A_SOMETHING_PAD)) Create a new attribute type which will use 32 bits at netlink level if value is small enough (probably most of the time?), and (4B-aligned) 64 bits otherwise. Kernel API is just: if (nla_put_uint(rsp, NETDEV_A_SOMETHING_SOMETHING, value)) Calling this new type "just" sint / uint with no specific size will hopefully also make people more comfortable with using it. Currently telling people "don't use u8, you may need the bits, and netlink will round up to 4B, anyway" is the #1 comment we give to newcomers. In terms of netlink layout it looks like this: 0 4 8 12 16 32b: [nlattr][ u32 ] 64b: [ pad ][nlattr][ u64 ] uint(32) [nlattr][ u32 ] uint(64) [nlattr][ u64 ] Signed-off-by: Jakub Kicinski Acked-by: Nicolas Dichtel Signed-off-by: David S. Miller

docs: netlink: clarify the historical baggage of Netlink flags

2022-09-30T01:39:39+00:00

nlmsg_flags are full of historical baggage, inconsistencies and strangeness. Try to document it more thoroughly. Explain the meaning of the ECHO flag (and while at it clarify the comment in the uAPI). Handwave a little about the NEW request flags and how they make sense on the surface but cater to really old paradigm before commands were a thing. I will add more notes on how to make use of ECHO and discouragement for reuse of flags to the kernel-side documentation. Link: https://lore.kernel.org/r/20220927212306.823862-1-kuba@kernel.org Signed-off-by: Jakub Kicinski

netlink: add support for ext_ack missing attributes

2022-08-30T10:20:43+00:00

There is currently no way to report via extack in a structured way that an attribute is missing. This leads to families resorting to string messages. Add a pair of attributes - @offset and @type for machine-readable way of reporting missing attributes. The @offset points to the nest which should have contained the attribute, @type is the expected nla_type. The offset will be skipped if the attribute is missing at the message level rather than inside a nest. User space should be able to figure out which attribute enum (AKA attribute space AKA attribute set) the nest pointed to by @offset is using. Reviewed-by: Johannes Berg Signed-off-by: Jakub Kicinski Signed-off-by: Paolo Abeni

net: improve and fix netlink kdoc

2022-08-23T23:10:23+00:00

Subsequent patch will render the kdoc from include/uapi/linux/netlink.h into Documentation. We need to fix the warnings. While at it move the comments on struct nlmsghdr to a proper kdoc comment. Link: https://lore.kernel.org/r/20220819200221.422801-1-kuba@kernel.org Signed-off-by: Jakub Kicinski

Remove DECnet support from kernel

2022-08-22T13:26:30+00:00

DECnet is an obsolete network protocol that receives more attention from kernel janitors than users. It belongs in computer protocol history museum not in Linux kernel. It has been "Orphaned" in kernel since 2010. The iproute2 support for DECnet was dropped in 5.0 release. The documentation link on Sourceforge says it is abandoned there as well. Leave the UAPI alone to keep userspace programs compiling. This means that there is still an empty neighbour table for AF_DECNET. The table of /proc/sys/net entries was updated to match current directories and reformatted to be alphabetical. Signed-off-by: Stephen Hemminger Acked-by: David Ahern Acked-by: Nikolay Aleksandrov Signed-off-by: David S. Miller

net: netlink: add NLM_F_BULK delete request modifier

2022-04-13T11:46:26+00:00

Add a new delete request modifier called NLM_F_BULK which, when supported, would cause the request to delete multiple objects. The flag is a convenient way to signal that a multiple delete operation is requested which can be gradually added to different delete requests. In order to make sure older kernels will error out if the operation is not supported instead of doing something unintended we have to break a required condition when implementing support for this flag, f.e. for neighbors we will omit the mandatory mac address attribute. Initially it will be used to add flush with filtering support for bridge fdbs, but it also opens the door to add similar support to others. Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller

netlink: simplify NLMSG_DATA with NLMSG_HDRLEN

2021-06-10T19:51:33+00:00

The NLMSG_LENGTH(0) may confuse the API users, NLMSG_HDRLEN is much more clear. Besides, some code style problems are also fixed. Signed-off-by: Chen Li Signed-off-by: David S. Miller

uapi: move constants from to

2020-12-15T20:13:36+00:00

and include in UAPI headers instead of . The reason is to avoid indirect include when using some network headers: or others -> -> . This indirect include causes on MUSL redefinition of struct sysinfo when included both and some of UAPI headers: In file included from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/kernel.h:5, from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/netlink.h:5, from ../include/tst_netlink.h:14, from tst_crypto.c:13: x86_64-buildroot-linux-musl/sysroot/usr/include/linux/sysinfo.h:8:8: error: redefinition of `struct sysinfo' struct sysinfo { ^~~~~~~ In file included from ../include/tst_safe_macros.h:15, from ../include/tst_test.h:93, from tst_crypto.c:11: x86_64-buildroot-linux-musl/sysroot/usr/include/sys/sysinfo.h:10:8: note: originally defined here Link: https://lkml.kernel.org/r/20201015190013.8901-1-petr.vorel@gmail.com Signed-off-by: Petr Vorel Suggested-by: Rich Felker Acked-by: Rich Felker Cc: Peter Korsgaard Cc: Baruch Siach Cc: Florian Weimer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

netlink: export policy in extended ACK

2020-10-10T03:22:32+00:00

Add a new attribute NLMSGERR_ATTR_POLICY to the extended ACK to advertise the policy, e.g. if an attribute was out of range, you'll know the range that's permissible. Add new NL_SET_ERR_MSG_ATTR_POL() and NL_SET_ERR_MSG_ATTR_POL() macros to set this, since realistically it's only useful to do this when the bad attribute (offset) is also returned. Use it in lib/nlattr.c which practically does all the policy validation. v2: - add and use netlink_policy_dump_attr_size_estimate() v3: - remove redundant break v4: - really remove redundant break ... sorry Reviewed-by: Jakub Kicinski Signed-off-by: Johannes Berg Signed-off-by: Jakub Kicinski

netlink: add mask validation

2020-10-06T13:25:55+00:00

We don't have good validation policy for existing unsigned int attrs which serve as flags (for new ones we could use NLA_BITFIELD32). With increased use of policy dumping having the validation be expressed as part of the policy is important. Add validation policy in form of a mask of supported/valid bits. Support u64 in the uAPI to be future-proof, but really for now the embedded mask member can only hold 32 bits, so anything with bit 32+ set will always fail validation. Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller