[PATCH net-next] sk-filter: Add ability to get socket filter program (v2)

All of lore.kernel.org
 help / color / mirror / Atom feed

From: Pavel Emelyanov <xemul@parallels.com>
To: David Miller <davem@davemloft.net>,
	Linux Netdev List <netdev@vger.kernel.org>
Subject: [PATCH net-next] sk-filter: Add ability to get socket filter program (v2)
Date: Thu, 01 Nov 2012 16:01:48 +0400	[thread overview]
Message-ID: <509264AC.5090802@parallels.com> (raw)

The SO_ATTACH_FILTER option is set only. I propose to add the get
ability by using SO_ATTACH_FILTER in getsockopt. To be less
irritating to eyes the SO_GET_FILTER alias to it is declared. This
ability is required by checkpoint-restore project to be able to 
save full state of a socket. 


There are two issues with getting filter back.

First, kernel modifies the sock_filter->code on filter load, thus in
order to return the filter element back to user we have to decode it
into user-visible constants. Fortunately the modification in question
is interconvertible.

Second, the BPF_S_ALU_DIV_K code modifies the command argument k to
speed up the run-time division by doing kernel_k = reciprocal(user_k).
Bad news is that different user_k may result in same kernel_k, so we 
can't get the original user_k back. Good news is that we don't have 
to do it. What we need to is calculate a user2_k so, that

  reciprocal(user2_k) == reciprocal(user_k) == kernel_k

i.e. if it's re-loaded back the compiled again value will be exactly
the same as it was. That said, the user2_k can be calculated like this

  user2_k = reciprocal(kernel_k)

with an exception, that if kernel_k == 0, then user2_k == 1.


The optlen argument is treated like this -- when zero, kernel returns
the amount of sock_fprog elements in filter, otherwise it should be
large enough for the sock_fprog array.

changes since v1:
* Declared SO_GET_FILTER in all arch headers
* Added decode of vlan-tag codes

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

---

diff --git a/arch/alpha/include/asm/socket.h b/arch/alpha/include/asm/socket.h
index 7d2f75b..0087d05 100644
--- a/arch/alpha/include/asm/socket.h
+++ b/arch/alpha/include/asm/socket.h
@@ -47,6 +47,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/arch/avr32/include/uapi/asm/socket.h b/arch/avr32/include/uapi/asm/socket.h
index a473f8c..486df68 100644
--- a/arch/avr32/include/uapi/asm/socket.h
+++ b/arch/avr32/include/uapi/asm/socket.h
@@ -40,6 +40,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/arch/cris/include/asm/socket.h b/arch/cris/include/asm/socket.h
index ae52825..b681b04 100644
--- a/arch/cris/include/asm/socket.h
+++ b/arch/cris/include/asm/socket.h
@@ -42,6 +42,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP           29
diff --git a/arch/frv/include/uapi/asm/socket.h b/arch/frv/include/uapi/asm/socket.h
index a5b1d7d..871f89b 100644
--- a/arch/frv/include/uapi/asm/socket.h
+++ b/arch/frv/include/uapi/asm/socket.h
@@ -40,6 +40,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME             28
 #define SO_TIMESTAMP		29
diff --git a/arch/h8300/include/asm/socket.h b/arch/h8300/include/asm/socket.h
index ec4554e..90a2e57 100644
--- a/arch/h8300/include/asm/socket.h
+++ b/arch/h8300/include/asm/socket.h
@@ -40,6 +40,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME             28
 #define SO_TIMESTAMP		29
diff --git a/arch/ia64/include/uapi/asm/socket.h b/arch/ia64/include/uapi/asm/socket.h
index 41fc28a..23d6759 100644
--- a/arch/ia64/include/uapi/asm/socket.h
+++ b/arch/ia64/include/uapi/asm/socket.h
@@ -49,6 +49,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER	26
 #define SO_DETACH_FILTER	27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/arch/m32r/include/asm/socket.h b/arch/m32r/include/asm/socket.h
index a15f40b..5e7088a 100644
--- a/arch/m32r/include/asm/socket.h
+++ b/arch/m32r/include/asm/socket.h
@@ -40,6 +40,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/arch/m68k/include/asm/socket.h b/arch/m68k/include/asm/socket.h
index d1be684..285da3b 100644
--- a/arch/m68k/include/asm/socket.h
+++ b/arch/m68k/include/asm/socket.h
@@ -40,6 +40,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME             28
 #define SO_TIMESTAMP		29
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index c5ed595..17307ab 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -63,6 +63,7 @@ To add: #define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME             28
 #define SO_TIMESTAMP		29
diff --git a/arch/mn10300/include/uapi/asm/socket.h b/arch/mn10300/include/uapi/asm/socket.h
index 820463a..af5366b 100644
--- a/arch/mn10300/include/uapi/asm/socket.h
+++ b/arch/mn10300/include/uapi/asm/socket.h
@@ -40,6 +40,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/arch/parisc/include/asm/socket.h b/arch/parisc/include/asm/socket.h
index 1b52c2c..d9ff473 100644
--- a/arch/parisc/include/asm/socket.h
+++ b/arch/parisc/include/asm/socket.h
@@ -48,6 +48,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        0x401a
 #define SO_DETACH_FILTER        0x401b
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_ACCEPTCONN		0x401c
 
diff --git a/arch/powerpc/include/uapi/asm/socket.h b/arch/powerpc/include/uapi/asm/socket.h
index 3d5179b..eb0b186 100644
--- a/arch/powerpc/include/uapi/asm/socket.h
+++ b/arch/powerpc/include/uapi/asm/socket.h
@@ -47,6 +47,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER	26
 #define SO_DETACH_FILTER	27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/arch/s390/include/uapi/asm/socket.h b/arch/s390/include/uapi/asm/socket.h
index 69718cd..436d07c 100644
--- a/arch/s390/include/uapi/asm/socket.h
+++ b/arch/s390/include/uapi/asm/socket.h
@@ -46,6 +46,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index bea1568..c83a937 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -41,6 +41,7 @@
 
 #define SO_ATTACH_FILTER	0x001a
 #define SO_DETACH_FILTER        0x001b
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		0x001c
 #define SO_TIMESTAMP		0x001d
diff --git a/arch/xtensa/include/asm/socket.h b/arch/xtensa/include/asm/socket.h
index e36c681..38079be 100644
--- a/arch/xtensa/include/asm/socket.h
+++ b/arch/xtensa/include/asm/socket.h
@@ -52,6 +52,7 @@
 
 #define SO_ATTACH_FILTER        26
 #define SO_DETACH_FILTER        27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/include/linux/filter.h b/include/linux/filter.h
index c9f0005..c45eabc 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -45,6 +45,7 @@ extern void sk_unattached_filter_destroy(struct sk_filter *fp);
 extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
 extern int sk_detach_filter(struct sock *sk);
 extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen);
+extern int sk_get_filter(struct sock *sk, struct sock_filter __user *filter, unsigned len);
 
 #ifdef CONFIG_BPF_JIT
 extern void bpf_jit_compile(struct sk_filter *fp);
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index b1bea03..2d32d07 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -43,6 +43,7 @@
 /* Socket filtering */
 #define SO_ATTACH_FILTER	26
 #define SO_DETACH_FILTER	27
+#define SO_GET_FILTER		SO_ATTACH_FILTER
 
 #define SO_PEERNAME		28
 #define SO_TIMESTAMP		29
diff --git a/net/core/filter.c b/net/core/filter.c
index 5a114d4..c23543c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -760,3 +760,133 @@ int sk_detach_filter(struct sock *sk)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(sk_detach_filter);
+
+static void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to)
+{
+	static const u16 decodes[] = {
+		[BPF_S_ALU_ADD_K]	= BPF_ALU|BPF_ADD|BPF_K,
+		[BPF_S_ALU_ADD_X]	= BPF_ALU|BPF_ADD|BPF_X,
+		[BPF_S_ALU_SUB_K]	= BPF_ALU|BPF_SUB|BPF_K,
+		[BPF_S_ALU_SUB_X]	= BPF_ALU|BPF_SUB|BPF_X,
+		[BPF_S_ALU_MUL_K]	= BPF_ALU|BPF_MUL|BPF_K,
+		[BPF_S_ALU_MUL_X]	= BPF_ALU|BPF_MUL|BPF_X,
+		[BPF_S_ALU_DIV_X]	= BPF_ALU|BPF_DIV|BPF_X,
+		[BPF_S_ALU_MOD_K]	= BPF_ALU|BPF_MOD|BPF_K,
+		[BPF_S_ALU_MOD_X]	= BPF_ALU|BPF_MOD|BPF_X,
+		[BPF_S_ALU_AND_K]	= BPF_ALU|BPF_AND|BPF_K,
+		[BPF_S_ALU_AND_X]	= BPF_ALU|BPF_AND|BPF_X,
+		[BPF_S_ALU_OR_K]	= BPF_ALU|BPF_OR|BPF_K,
+		[BPF_S_ALU_OR_X]	= BPF_ALU|BPF_OR|BPF_X,
+		[BPF_S_ALU_XOR_K]	= BPF_ALU|BPF_XOR|BPF_K,
+		[BPF_S_ALU_XOR_X]	= BPF_ALU|BPF_XOR|BPF_X,
+		[BPF_S_ALU_LSH_K]	= BPF_ALU|BPF_LSH|BPF_K,
+		[BPF_S_ALU_LSH_X]	= BPF_ALU|BPF_LSH|BPF_X,
+		[BPF_S_ALU_RSH_K]	= BPF_ALU|BPF_RSH|BPF_K,
+		[BPF_S_ALU_RSH_X]	= BPF_ALU|BPF_RSH|BPF_X,
+		[BPF_S_ALU_NEG]		= BPF_ALU|BPF_NEG,
+		[BPF_S_LD_W_ABS]	= BPF_LD|BPF_W|BPF_ABS,
+		[BPF_S_LD_H_ABS]	= BPF_LD|BPF_H|BPF_ABS,
+		[BPF_S_LD_B_ABS]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_PROTOCOL]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_PKTTYPE]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_IFINDEX]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_NLATTR]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_NLATTR_NEST]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_MARK]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_QUEUE]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_HATYPE]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_RXHASH]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_CPU]		= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_ALU_XOR_X]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_SECCOMP_LD_W] = BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_VLAN_TAG]	= BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_ANC_VLAN_TAG_PRESENT] = BPF_LD|BPF_B|BPF_ABS,
+		[BPF_S_LD_W_LEN]	= BPF_LD|BPF_W|BPF_LEN,
+		[BPF_S_LD_W_IND]	= BPF_LD|BPF_W|BPF_IND,
+		[BPF_S_LD_H_IND]	= BPF_LD|BPF_H|BPF_IND,
+		[BPF_S_LD_B_IND]	= BPF_LD|BPF_B|BPF_IND,
+		[BPF_S_LD_IMM]		= BPF_LD|BPF_IMM,
+		[BPF_S_LDX_W_LEN]	= BPF_LDX|BPF_W|BPF_LEN,
+		[BPF_S_LDX_B_MSH]	= BPF_LDX|BPF_B|BPF_MSH,
+		[BPF_S_LDX_IMM]		= BPF_LDX|BPF_IMM,
+		[BPF_S_MISC_TAX]	= BPF_MISC|BPF_TAX,
+		[BPF_S_MISC_TXA]	= BPF_MISC|BPF_TXA,
+		[BPF_S_RET_K]		= BPF_RET|BPF_K,
+		[BPF_S_RET_A]		= BPF_RET|BPF_A,
+		[BPF_S_ALU_DIV_K]	= BPF_ALU|BPF_DIV|BPF_K,
+		[BPF_S_LD_MEM]		= BPF_LD|BPF_MEM,
+		[BPF_S_LDX_MEM]		= BPF_LDX|BPF_MEM,
+		[BPF_S_ST]		= BPF_ST,
+		[BPF_S_STX]		= BPF_STX,
+		[BPF_S_JMP_JA]		= BPF_JMP|BPF_JA,
+		[BPF_S_JMP_JEQ_K]	= BPF_JMP|BPF_JEQ|BPF_K,
+		[BPF_S_JMP_JEQ_X]	= BPF_JMP|BPF_JEQ|BPF_X,
+		[BPF_S_JMP_JGE_K]	= BPF_JMP|BPF_JGE|BPF_K,
+		[BPF_S_JMP_JGE_X]	= BPF_JMP|BPF_JGE|BPF_X,
+		[BPF_S_JMP_JGT_K]	= BPF_JMP|BPF_JGT|BPF_K,
+		[BPF_S_JMP_JGT_X]	= BPF_JMP|BPF_JGT|BPF_X,
+		[BPF_S_JMP_JSET_K]	= BPF_JMP|BPF_JSET|BPF_K,
+		[BPF_S_JMP_JSET_X]	= BPF_JMP|BPF_JSET|BPF_X,
+	};
+	u16 code;
+
+	code = filt->code;
+
+	to->code = decodes[code];
+	to->jt = filt->jt;
+	to->jf = filt->jf;
+
+	if (code == BPF_S_ALU_DIV_K) {
+		/*
+		 * When loaded this rule user gave us X, which was
+		 * translated into R = r(X). Now we calculate the
+		 * RR = r(R) and report it back. If next time this
+		 * value is loaded and RRR = r(RR) is calculated
+		 * then the R == RRR will be true.
+		 *
+		 * One exception. X == 1 translates into R == 0 and
+		 * we can't calculate RR out of it with r().
+		 */
+
+		if (filt->k == 0)
+			to->k = 1;
+		else
+			to->k = reciprocal_value(filt->k);
+
+		BUG_ON(reciprocal_value(to->k) != filt->k);
+	} else
+		to->k = filt->k;
+}
+
+int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf, unsigned int len)
+{
+	struct sk_filter *filter;
+	int i, ret;
+
+	lock_sock(sk);
+	filter = rcu_dereference_protected(sk->sk_filter,
+			sock_owned_by_user(sk));
+	ret = 0;
+	if (!filter)
+		goto out;
+	ret = filter->len;
+	if (!len)
+		goto out;
+	ret = -EINVAL;
+	if (len < filter->len)
+		goto out;
+
+	ret = -EFAULT;
+	for (i = 0; i < filter->len; i++) {
+		struct sock_filter fb;
+
+		sk_decode_filter(&filter->insns[i], &fb);
+		if (copy_to_user(&ubuf[i], &fb, sizeof(fb)))
+			goto out;
+	}
+
+	ret = filter->len;
+out:
+	release_sock(sk);
+	return ret;
+}
diff --git a/net/core/sock.c b/net/core/sock.c
index 0a023b8..0628600 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1077,6 +1077,12 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 	case SO_BINDTODEVICE:
 		v.val = sk->sk_bound_dev_if;
 		break;
+	case SO_GET_FILTER:
+		len = sk_get_filter(sk, (struct sock_filter __user *)optval, len);
+		if (len < 0)
+			return len;
+
+		goto lenout;
 	default:
 		return -ENOPROTOOPT;
 	}

next             reply	other threads:[~2012-11-01 12:02 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-01 12:01 Pavel Emelyanov [this message]
2012-11-01 15:17 ` [PATCH net-next] sk-filter: Add ability to get socket filter program (v2) David Miller

find likely ancestor, descendant, or conflicting patches for this message:
( dfblob:7d2f75b dfblob:0087d05 dfblob:a473f8c dfblob:486df68
dfblob:ae52825 dfblob:b681b04 dfblob:a5b1d7d dfblob:871f89b
dfblob:ec4554e dfblob:90a2e57 dfblob:41fc28a dfblob:23d6759
dfblob:a15f40b dfblob:5e7088a dfblob:d1be684 dfblob:285da3b
dfblob:c5ed595 dfblob:17307ab dfblob:820463a dfblob:af5366b
dfblob:1b52c2c dfblob:d9ff473 dfblob:3d5179b dfblob:eb0b186
dfblob:69718cd dfblob:436d07c dfblob:bea1568 dfblob:c83a937
dfblob:e36c681 dfblob:38079be dfblob:c9f0005 dfblob:c45eabc
dfblob:b1bea03 dfblob:2d32d07 dfblob:5a114d4 dfblob:c23543c
dfblob:0a023b8 dfblob:0628600 )
 OR (
bs:"[PATCH net-next] sk-filter: Add ability to get socket filter program (v2)" )
	(help)

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=509264AC.5090802@parallels.com \
    --to=xemul@parallels.com \
    --cc=davem@davemloft.net \
    --cc=netdev@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Be sure your reply has a Subject: header at the top and a blank line before the message body.

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.