From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamal Hadi Salim Subject: [PATCH net-next RFC 1/1] net netlink: Add new type NLA_FLAG_BITS Date: Sun, 30 Apr 2017 10:28:39 -0400 Message-ID: <1493562519-15563-1-git-send-email-jhs@emojatatu.com> Cc: netdev@vger.kernel.org, jiri@resnulli.us, xiyou.wangcong@gmail.com, Jamal Hadi Salim To: davem@davemloft.net Return-path: Received: from mail-io0-f196.google.com ([209.85.223.196]:35191 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752633AbdD3O25 (ORCPT ); Sun, 30 Apr 2017 10:28:57 -0400 Received: by mail-io0-f196.google.com with SMTP id d203so17263347iof.2 for ; Sun, 30 Apr 2017 07:28:56 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: From: Jamal Hadi Salim 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. Example if the user tries to set a bit flag that is not understood then the _it will be rejected_. 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 (which should be a separate pach): a validation callback that could be speaciliazed for other types. So a kernel subsystem could specify validation rules of the following nature: [ATTR_GOO] = { .type = MYTYPE, .validation_data = &myvalidation_data, .validate_content = mycontent_validator }, 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; ... validate user_data against valid_data_constraint ... ... return appropriate error code etc ... } Only compile tested to float the idea. Signed-off-by: Jamal Hadi Salim --- 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 #include +struct nla_bit_flags { + u32 nla_flag_values; + u32 nla_flag_selector; +}; + /* ======================================================================== * 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 cce0613..3691d8d 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; + + + 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 */ + 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); + return 0; } -- 1.9.1