[PATCH] backports: netlink: add 64-bit aligned helper functions

[Arend van Spriel <arend@broadcom.com>]

This backports the following commits to support nl80211 changes:

089bf1a6a924 ("libnl: add more helpers to align attributes on 64-bit")
35c5845957c7 ("net: Add helpers for 64-bit aligning netlink attributes.")

Signed-off-by: Arend van Spriel <arend@broadcom.com>
---
 backport/backport-include/net/netlink.h |  83 +++++++++++++++++++++++
 backport/compat/Makefile                |   1 +
 backport/compat/backport-4.7.c          | 113 ++++++++++++++++++++++++++++++++
 3 files changed, 197 insertions(+)
 create mode 100644 backport/compat/backport-4.7.c

diff --git a/backport/backport-include/net/netlink.h b/backport/backport-include/net/netlink.h
index 40160b5..3513d5d 100644
--- a/backport/backport-include/net/netlink.h
+++ b/backport/backport-include/net/netlink.h
@@ -189,4 +189,87 @@ static inline __le64 nla_get_le64(const struct nlattr *nla)
 }
 #endif /* < 4.4 */
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4,7,0)
+/**
+ * nla_need_padding_for_64bit - test 64-bit alignment of the next attribute
+ * @skb: socket buffer the message is stored in
+ *
+ * Return true if padding is needed to align the next attribute (nla_data()) to
+ * a 64-bit aligned area.
+ */
+#define nla_need_padding_for_64bit LINUX_BACKPORT(nla_need_padding_for_64bit)
+static inline bool nla_need_padding_for_64bit(struct sk_buff *skb)
+{
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+       /* The nlattr header is 4 bytes in size, that's why we test
+        * if the skb->data _is_ aligned.  A NOP attribute, plus
+        * nlattr header for next attribute, will make nla_data()
+        * 8-byte aligned.
+        */
+       if (IS_ALIGNED((unsigned long)skb_tail_pointer(skb), 8))
+               return true;
+#endif
+       return false;
+}
+/**
+ * nla_align_64bit - 64-bit align the nla_data() of next attribute
+ * @skb: socket buffer the message is stored in
+ * @padattr: attribute type for the padding
+ *
+ * Conditionally emit a padding netlink attribute in order to make
+ * the next attribute we emit have a 64-bit aligned nla_data() area.
+ * This will only be done in architectures which do not have
+ * HAVE_EFFICIENT_UNALIGNED_ACCESS defined.
+ *
+ * Returns zero on success or a negative error code.
+ */
+#define nla_align_64bit LINUX_BACKPORT(nla_align_64bit)
+static inline int nla_align_64bit(struct sk_buff *skb, int padattr)
+{
+       if (nla_need_padding_for_64bit(skb) &&
+            !nla_reserve(skb, padattr, 0))
+                return -EMSGSIZE;
+       return 0;
+}
+
+/**
+ * nla_total_size_64bit - total length of attribute including padding
+ * @payload: length of payload
+ */
+#define nla_total_size_64bit LINUX_BACKPORT(nla_total_size_64bit)
+static inline int nla_total_size_64bit(int payload)
+{
+       return NLA_ALIGN(nla_attr_size(payload))
+#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS
+               + NLA_ALIGN(nla_attr_size(0))
+#endif
+               ;
+}
+#define __nla_reserve_64bit LINUX_BACKPORT(__nla_reserve_64bit)
+struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
+				   int attrlen, int padattr);
+#define nla_reserve_64bit LINUX_BACKPORT(nla_reserve_64bit)
+struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype,
+				 int attrlen, int padattr);
+#define __nla_put_64bit LINUX_BACKPORT(__nla_put_64bit)
+void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+		     const void *data, int padattr);
+#define nla_put_64bit LINUX_BACKPORT(nla_put_64bit)
+int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+		  const void *data, int padattr);
+/**
+ * nla_put_u64_64bit - Add a u64 netlink attribute to a skb and align it
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @value: numeric value
+ * @padattr: attribute type for the padding
+ */
+#define nla_put_u64_64bit LINUX_BACKPORT(nla_put_u64_64bit)
+static inline int nla_put_u64_64bit(struct sk_buff *skb, int attrtype,
+                                    u64 value, int padattr)
+{
+        return nla_put_64bit(skb, attrtype, sizeof(u64), &value, padattr);
+}
+#endif /* < 4.7 */
+
 #endif /* __BACKPORT_NET_NETLINK_H */
diff --git a/backport/compat/Makefile b/backport/compat/Makefile
index 7651f83..6013083 100644
--- a/backport/compat/Makefile
+++ b/backport/compat/Makefile
@@ -32,6 +32,7 @@ compat-$(CPTCFG_KERNEL_4_3) += backport-4.3.o
 compat-$(CPTCFG_KERNEL_4_4) += backport-4.4.o
 compat-$(CPTCFG_KERNEL_4_5) += backport-4.5.o
 compat-$(CPTCFG_KERNEL_4_6) += backport-4.6.o
+compat-$(CPTCFG_KERNEL_4_7) += backport-4.7.o
 
 compat-$(CPTCFG_BPAUTO_BUILD_CRYPTO_CCM) += crypto-ccm.o
 compat-$(CPTCFG_BPAUTO_CRYPTO_SKCIPHER) += crypto-skcipher.o
diff --git a/backport/compat/backport-4.7.c b/backport/compat/backport-4.7.c
new file mode 100644
index 0000000..4edc4e8
--- /dev/null
+++ b/backport/compat/backport-4.7.c
@@ -0,0 +1,113 @@
+/*
+ * Copyright(c) 2016 Hauke Mehrtens <hauke@hauke-m.de>
+ *
+ * Backport functionality introduced in Linux 4.7.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+ #include <linux/skbuff.h>
+ #include <net/netlink.h>
+
+ /**
+ * __nla_reserve_64bit - reserve room for attribute on the skb and align it
+ * @skb: socket buffer to reserve room on
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ *
+ * Adds a netlink attribute header to a socket buffer and reserves
+ * room for the payload but does not copy it. It also ensure that this
+ * attribute will be 64-bit aign.
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the attribute header and payload.
+ */
+struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
+                                  int attrlen, int padattr)
+{
+       if (nla_need_padding_for_64bit(skb))
+               nla_align_64bit(skb, padattr);
+
+       return __nla_reserve(skb, attrtype, attrlen);
+}
+EXPORT_SYMBOL_GPL(__nla_reserve_64bit);
+
+ /**
+ * nla_reserve_64bit - reserve room for attribute on the skb and align it
+ * @skb: socket buffer to reserve room on
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ *
+ * Adds a netlink attribute header to a socket buffer and reserves
+ * room for the payload but does not copy it. It also ensure that this
+ * attribute will be 64-bit aign.
+ *
+ * Returns NULL if the tailroom of the skb is insufficient to store
+ * the attribute header and payload.
+ */
+struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+				 int padattr)
+{
+       size_t len;
+
+       if (nla_need_padding_for_64bit(skb))
+               len = nla_total_size_64bit(attrlen);
+       else
+               len = nla_total_size(attrlen);
+       if (unlikely(skb_tailroom(skb) < len))
+               return NULL;
+
+       return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
+}
+EXPORT_SYMBOL_GPL(nla_reserve_64bit);
+
+ /**
+ * __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the attribute header and payload.
+ */
+void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+                    const void *data, int padattr)
+{
+       struct nlattr *nla;
+
+       nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
+       memcpy(nla_data(nla), data, attrlen);
+}
+EXPORT_SYMBOL_GPL(__nla_put_64bit);
+
+ /**
+ * nla_put_64bit - Add a netlink attribute to a socket buffer and align it
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
+ * the attribute header and payload.
+ */
+int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+                 const void *data, int padattr)
+{
+       size_t len;
+
+       if (nla_need_padding_for_64bit(skb))
+               len = nla_total_size_64bit(attrlen);
+       else
+               len = nla_total_size(attrlen);
+       if (unlikely(skb_tailroom(skb) < len))
+               return -EMSGSIZE;
+
+       __nla_put_64bit(skb, attrtype, attrlen, data, padattr);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(nla_put_64bit);
+
-- 
1.9.1

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