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Date: Sun, 11 Jun 2017 15:49:24 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jamal Hadi Salim <jhs@...atatu.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
xiyou.wangcong@...il.com, eric.dumazet@...il.com,
simon.horman@...ronome.com, mrv@...atatu.com
Subject: Re: [PATCH net-next v10 1/4] net netlink: Add new type NLA_FLAG_BITS
Sun, Jun 11, 2017 at 01:53:43PM CEST, jhs@...atatu.com wrote:
>From: Jamal Hadi Salim <jhs@...atatu.com>
>
>Generic bitflags attribute content sent to the kernel by user.
>With this type the user can either set or unset a flag in the
>kernel.
>
>The nla_flag_values is a bitmap that defines the values being set
>The nla_flag_selector is a bitmask that defines which value is legit.
>
>A check is made to ensure the rules that a kernel subsystem always
>conforms to bitflags the kernel already knows about. i.e
>if the user tries to set a bit flag that is not understood then
>the _it will be rejected_.
>
>In the most basic form, the user specifies the attribute policy as:
>[ATTR_GOO] = { .type = NLA_FLAG_BITS, .validation_data = &myvalidflags },
>
>where myvalidflags is the bit mask of the flags the kernel understands.
>
>If the user _does not_ provide myvalidflags then the attribute will
>also be rejected.
>
>Examples:
>nla_flag_values = 0x0, and nla_flag_selector = 0x1
>implies we are selecting bit 1 and we want to set its value to 0.
>
>nla_flag_values = 0x2, and nla_flag_selector = 0x2
>implies we are selecting bit 2 and we want to set its value to 1.
>
>This patch also provides an extra feature: a validation callback
>that could be speaciliazed for other types.
s/speaciliazed/speciliazed/
>This feature is intended to be used by a kernel subsystem to check
>for a combination of bits being present. Example "bit x is valid
>only if bit y and z are present".
>
>So a kernel subsystem could specify validation rules of the following
>nature:
>
>[ATTR_GOO] = { .type = MYTYPE,
> .validation_data = &myvalidation_data,
> .validate_content = mycontent_validator },
Indent is wrong. (Does not matter really in desc, but anyway)
>
>With validator callback looking like:
>
>int mycontent_validator(const struct nlattr *nla, void *valid_data)
>{
> const struct myattribute *user_data = nla_data(nla);
> struct myvalidation_struct *valid_data_constraint = valid_data;
>
> ... return appropriate error code etc ...
>}
>
>
>Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
Suggested-by: Jiri Pirko <jiri@...lanox.com>
>---
> include/net/netlink.h | 11 +++++++++++
> include/uapi/linux/rtnetlink.h | 17 +++++++++++++++++
> lib/nlattr.c | 25 +++++++++++++++++++++++++
> 3 files changed, 53 insertions(+)
>
>diff --git a/include/net/netlink.h b/include/net/netlink.h
>index 0170917..8ab9784 100644
>--- a/include/net/netlink.h
>+++ b/include/net/netlink.h
>@@ -6,6 +6,11 @@
> #include <linux/jiffies.h>
> #include <linux/in6.h>
>
>+struct nla_bit_flags {
>+ u32 nla_flag_values;
>+ u32 nla_flag_selector;
>+};
I don't understand why you redefine the struct here. You already have it
defined in the uapi: struct __nla_bit_flags
Just move this (struct nla_bit_flags) to the uapi and remove
__nla_bit_flags ?
>+
> /* ========================================================================
> * Netlink Messages and Attributes Interface (As Seen On TV)
> * ------------------------------------------------------------------------
>@@ -178,6 +183,7 @@ enum {
> NLA_S16,
> NLA_S32,
> NLA_S64,
>+ NLA_FLAG_BITS,
> __NLA_TYPE_MAX,
> };
>
>@@ -206,6 +212,7 @@ enum {
> * NLA_MSECS Leaving the length field zero will verify the
> * given type fits, using it verifies minimum length
> * just like "All other"
>+ * NLA_FLAG_BITS A bitmap/bitselector attribute
> * All other Minimum length of attribute payload
> *
> * Example:
>@@ -213,11 +220,15 @@ enum {
> * [ATTR_FOO] = { .type = NLA_U16 },
> * [ATTR_BAR] = { .type = NLA_STRING, .len = BARSIZ },
> * [ATTR_BAZ] = { .len = sizeof(struct mystruct) },
>+ * [ATTR_GOO] = { .type = NLA_FLAG_BITS, .validation_data = &myvalidflags },
> * };
> */
> struct nla_policy {
> u16 type;
> u16 len;
>+ void *validation_data;
>+ int (*validate_content)(const struct nlattr *nla,
>+ const void *validation_data);
> };
>
> /**
>diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
>index 564790e..8f07957 100644
>--- a/include/uapi/linux/rtnetlink.h
>+++ b/include/uapi/linux/rtnetlink.h
>@@ -179,6 +179,23 @@ struct rtattr {
> #define RTA_DATA(rta) ((void*)(((char*)(rta)) + RTA_LENGTH(0)))
> #define RTA_PAYLOAD(rta) ((int)((rta)->rta_len) - RTA_LENGTH(0))
>
>+/* Generic bitflags attribute content sent to the kernel.
>+ *
>+ * The nla_flag_values is a bitmap that defines the values being set
>+ * The nla_flag_selector is a bitmask that defines which value is legit
>+ *
>+ * Examples:
>+ * nla_flag_values = 0x0, and nla_flag_selector = 0x1
>+ * implies we are selecting bit 1 and we want to set its value to 0.
>+ *
>+ * nla_flag_values = 0x2, and nla_flag_selector = 0x2
>+ * implies we are selecting bit 2 and we want to set its value to 1.
>+ *
>+ */
>+struct __nla_bit_flags {
>+ __u32 nla_flag_values;
>+ __u32 nla_flag_selector;
>+};
>
>
>
>diff --git a/lib/nlattr.c b/lib/nlattr.c
>index a7e0b16..78fed43 100644
>--- a/lib/nlattr.c
>+++ b/lib/nlattr.c
>@@ -27,6 +27,21 @@
> [NLA_S64] = sizeof(s64),
> };
>
>+static int validate_nla_bit_flags(const struct nlattr *nla, void *valid_data)
>+{
>+ const struct nla_bit_flags *nbf = nla_data(nla);
>+ u32 *valid_flags_mask = valid_data;
>+
>+ if (!valid_data)
>+ return -EINVAL;
>+
>+
Avoid one empty line here (you have 2)
>+ if (nbf->nla_flag_values & ~*valid_flags_mask)
>+ return -EINVAL;
>+
>+ return 0;
>+}
>+
> static int validate_nla(const struct nlattr *nla, int maxtype,
> const struct nla_policy *policy)
> {
>@@ -46,6 +61,13 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
> return -ERANGE;
> break;
>
>+ case NLA_FLAG_BITS:
>+ if (attrlen != 8) /* 2 x 32 bits */
sizeof(struct nla_bit_flags) instead of 8 please, you can skip the
comment then.
>+ return -ERANGE;
>+
>+ return validate_nla_bit_flags(nla, pt->validation_data);
>+ break;
>+
> case NLA_NUL_STRING:
> if (pt->len)
> minlen = min_t(int, attrlen, pt->len + 1);
>@@ -103,6 +125,9 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
> return -ERANGE;
> }
>
>+ if (pt->validate_content)
>+ return pt->validate_content(nla, pt->validation_data);
This validation mechanism is completely independent from the added NLA_FLAG_BITS
attr as it could be used with other attribute types. Please have it as a
separate patch.
>+
> return 0;
> }
>
>--
>1.9.1
>
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