From ceae98914962e4375a98db2622b65ecf44b0232a Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman@redhat.com>
Date: Tue, 19 Mar 2013 16:36:10 +0100
Subject: [PATCH] bpfc: filter: add poff ancillary operation

In preparation for [1], add the #poff operation, so that users can
dynamically truncate packets on the payload start offset. This is
useful for several reasons: privacy, speed, ...

Example for bpfc:

  ld #poff
  ret a

  [1] http://thread.gmane.org/gmane.linux.network/262512

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
---
 bpf.h        |  3 +++
 bpf_lexer.l  |  1 +
 bpf_parser.y | 11 ++++++++++-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/bpf.h b/bpf.h
index 84cf0b87..07631d62 100644
--- a/bpf.h
+++ b/bpf.h
@@ -131,5 +131,8 @@ static inline void bpf_release(struct sock_fprog *bpf)
 #ifndef SKF_AD_VLAN_TAG_PRESENT
 # define SKF_AD_VLAN_TAG_PRESENT	48
 #endif
+#ifndef SKF_AD_PAY_OFFSET
+# define SKF_AD_PAY_OFFSET		52
+#endif
 
 #endif /* BPF_I_H */
diff --git a/bpf_lexer.l b/bpf_lexer.l
index d4b6947b..a2ff90ae 100644
--- a/bpf_lexer.l
+++ b/bpf_lexer.l
@@ -75,6 +75,7 @@ label		[a-zA-Z_][a-zA-Z0-9_]+
 "#"?("len"|"pktlen")	{ return K_PKT_LEN; }
 "#"?("pto"|"proto")	{ return K_PROTO; }
 "#"?("type")		{ return K_TYPE; }
+"#"?("poff")		{ return K_POFF; }
 "#"?("ifx"|"ifidx")	{ return K_IFIDX; }
 "#"?("nla")		{ return K_NLATTR; }
 "#"?("nlan")		{ return K_NLATTR_NEST; }
diff --git a/bpf_parser.y b/bpf_parser.y
index 7f6bcc80..459ea99f 100644
--- a/bpf_parser.y
+++ b/bpf_parser.y
@@ -132,7 +132,7 @@ static int find_intr_offset_or_panic(char *label_to_search)
 %token OP_LDXI
 
 %token K_PKT_LEN K_PROTO K_TYPE K_NLATTR K_NLATTR_NEST K_MARK K_QUEUE K_HATYPE
-%token K_RXHASH K_CPU K_IFIDX K_VLANT K_VLANP
+%token K_RXHASH K_CPU K_IFIDX K_VLANT K_VLANP K_POFF
 
 %token ':' ',' '[' ']' '(' ')' 'x' 'a' '+' 'M' '*' '&' '#'
 
@@ -235,6 +235,9 @@ ldb
 	| OP_LDB K_VLANP {
 		set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 			       SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT); }
+	| OP_LDB K_POFF {
+		set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+			       SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
 	;
 
 ldh
@@ -278,6 +281,9 @@ ldh
 	| OP_LDH K_VLANP {
 		set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 			       SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT); }
+	| OP_LDH K_POFF {
+		set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+			       SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
 	;
 
 ldi
@@ -326,6 +332,9 @@ ld
 	| OP_LD K_VLANP {
 		set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 			       SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT); }
+	| OP_LD K_POFF {
+		set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+			       SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
 	| OP_LD 'M' '[' number ']' {
 		set_curr_instr(BPF_LD | BPF_MEM, 0, 0, $4); }
 	| OP_LD '[' 'x' '+' number ']' {
-- 
2.11.4.GIT