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Message-ID: <20230223175708.51e593f0@kernel.org>
Date: Thu, 23 Feb 2023 17:57:08 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: stephen@...workplumber.org
Cc: dsahern@...il.com, jhs@...atatu.com, netdev@...r.kernel.org,
Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH iproute2] genl: print caps for all families
On Thu, 23 Feb 2023 17:52:34 -0800 Jakub Kicinski wrote:
> Back in 2006 kernel commit 334c29a64507 ("[GENETLINK]: Move
> command capabilities to flags.") removed some attributes and
> moved the capabilities to flags. Corresponding iproute2
> commit 26328fc3933f ("Add controller support for new features
> exposed") added the ability to print those caps.
>
> Printing is gated on version of the family, but we're checking
> the version of each individual family rather than the control
> family. The format of attributes in the control family
> is dictated by the version of the control family alone.
>
> Families can't use flags for random things, anyway,
> because kernel core has a fixed interpretation.
>
> Thanks to this change caps will be shown for all families
> (assuming kernel newer than 2.6.19), not just those which
> by coincidence have their local version >= 2.
>
> For instance devlink, before:
>
> $ genl ctrl get name devlink
> Name: devlink
> ID: 0x15 Version: 0x1 header size: 0 max attribs: 179
> commands supported:
> #1: ID-0x1
> #2: ID-0x5
> #3: ID-0x6
> ...
>
> after:
>
> $ genl ctrl get name devlink
> Name: devlink
> ID: 0x15 Version: 0x1 header size: 0 max attribs: 179
> commands supported:
> #1: ID-0x1
> Capabilities (0xe):
> can doit; can dumpit; has policy
>
> #2: ID-0x5
> Capabilities (0xe):
> can doit; can dumpit; has policy
>
> #3: ID-0x6
> Capabilities (0xb):
> requires admin permission; can doit; has policy
>
> Leave ctrl_v as 0 if we fail to read the version. Old code used 1
> as the default, but 0 or 1 - does not matter, checks are for >= 2.
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> Not really sure if this is a fix or not..
Adding Johannes, that's probably everyone who ever used this
command on CC? ;)
> diff --git a/genl/ctrl.c b/genl/ctrl.c
> index a2d87af0ad07..1fcb3848f137 100644
> --- a/genl/ctrl.c
> +++ b/genl/ctrl.c
> @@ -21,6 +21,8 @@
> #define GENL_MAX_FAM_OPS 256
> #define GENL_MAX_FAM_GRPS 256
>
> +static unsigned int ctrl_v;
> +
> static int usage(void)
> {
> fprintf(stderr,"Usage: ctrl <CMD>\n" \
> @@ -109,7 +111,6 @@ static int print_ctrl(struct rtnl_ctrl_data *ctrl,
> int len = n->nlmsg_len;
> struct rtattr *attrs;
> FILE *fp = (FILE *) arg;
> - __u32 ctrl_v = 0x1;
>
> if (n->nlmsg_type != GENL_ID_CTRL) {
> fprintf(stderr, "Not a controller message, nlmsg_len=%d "
> @@ -148,7 +149,6 @@ static int print_ctrl(struct rtnl_ctrl_data *ctrl,
> if (tb[CTRL_ATTR_VERSION]) {
> __u32 *v = RTA_DATA(tb[CTRL_ATTR_VERSION]);
> fprintf(fp, " Version: 0x%x ",*v);
> - ctrl_v = *v;
> }
> if (tb[CTRL_ATTR_HDRSIZE]) {
> __u32 *h = RTA_DATA(tb[CTRL_ATTR_HDRSIZE]);
> @@ -241,6 +241,55 @@ static int print_ctrl2(struct nlmsghdr *n, void *arg)
> return print_ctrl(NULL, n, arg);
> }
>
> +static void ctrl_load_ctrl_version(struct rtnl_handle *rth)
> +{
> + struct rtattr *tb[CTRL_ATTR_MAX + 1];
> + struct genlmsghdr *ghdr;
> + struct rtattr *attrs;
> + struct {
> + struct nlmsghdr n;
> + struct genlmsghdr g;
> + char buf[128];
> + } req = {
> + .n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN),
> + .n.nlmsg_flags = NLM_F_REQUEST,
> + .n.nlmsg_type = GENL_ID_CTRL,
> + .g.cmd = CTRL_CMD_GETFAMILY,
> + };
> + struct nlmsghdr *nlh = &req.n;
> + struct nlmsghdr *answer = NULL;
> + __u16 id = GENL_ID_CTRL;
> + int len;
> +
> + addattr_l(nlh, 128, CTRL_ATTR_FAMILY_ID, &id, 2);
> +
> + if (rtnl_talk(rth, nlh, &answer) < 0) {
> + fprintf(stderr, "Error talking to the kernel\n");
> + return;
> + }
> +
> + ghdr = NLMSG_DATA(answer);
> + if (answer->nlmsg_type != GENL_ID_CTRL ||
> + ghdr->cmd != CTRL_CMD_NEWFAMILY) {
> + fprintf(stderr, "Unexpected reply nlmsg_type=%u cmd=%u\n",
> + answer->nlmsg_type, ghdr->cmd);
> + return;
> + }
> +
> + len = answer->nlmsg_len;
> + len -= NLMSG_LENGTH(GENL_HDRLEN);
> + if (len < 0) {
> + fprintf(stderr, "wrong controller message len %d\n", len);
> + return;
> + }
> +
> + attrs = (struct rtattr *) ((char *) ghdr + GENL_HDRLEN);
> + parse_rtattr_flags(tb, CTRL_ATTR_MAX, attrs, len, NLA_F_NESTED);
> +
> + if (tb[CTRL_ATTR_VERSION])
> + ctrl_v = rta_getattr_u16(tb[CTRL_ATTR_VERSION]);
> +}
> +
> static int ctrl_list(int cmd, int argc, char **argv)
> {
> struct rtnl_handle rth;
> @@ -264,6 +313,9 @@ static int ctrl_list(int cmd, int argc, char **argv)
> exit(1);
> }
>
> + if (!ctrl_v)
> + ctrl_load_ctrl_version(&rth);
> +
> if (cmd == CTRL_CMD_GETFAMILY || cmd == CTRL_CMD_GETPOLICY) {
> req.g.cmd = cmd;
>
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