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之前的版本是这样:
#ifndef __KERNEL__
/* IP Cache bits. */
/* Src IP address. */
#define NFC_IP_SRC 0x0001
/* Dest IP address. */
#define NFC_IP_DST 0x0002
/* Input device. */
#define NFC_IP_IF_IN 0x0004
/* Output device. */
#define NFC_IP_IF_OUT 0x0008
/* TOS. */
#define NFC_IP_TOS 0x0010
/* Protocol. */
#define NFC_IP_PROTO 0x0020
/* IP options. */
#define NFC_IP_OPTIONS 0x0040
/* Frag & flags. */
#define NFC_IP_FRAG 0x0080
/* Per-protocol information: only matters if proto match. */
/* TCP flags. */
#define NFC_IP_TCPFLAGS 0x0100
/* Source port. */
#define NFC_IP_SRC_PT 0x0200
/* Dest port. */
#define NFC_IP_DST_PT 0x0400
/* Something else about the proto */
#define NFC_IP_PROTO_UNKNOWN 0x2000
#endif /* ! __KERNEL__ */
/* IP Hooks */
/* After promisc drops, checksum checks. */
#define NF_IP_PRE_ROUTING 0
/* If the packet is destined for this box. */
#define NF_IP_LOCAL_IN 1
/* If the packet is destined for another interface. */
#define NF_IP_FORWARD 2
/* Packets coming from a local process. */
#define NF_IP_LOCAL_OUT 3
/* Packets about to hit the wire. */
#define NF_IP_POST_ROUTING 4
#define NF_IP_NUMHOOKS 5
但在2.6.25中变成了:
#ifndef __KERNEL__
/* IP Cache bits. */
/* Src IP address. */
#define NFC_IP_SRC 0x0001
/* Dest IP address. */
#define NFC_IP_DST 0x0002
/* Input device. */
#define NFC_IP_IF_IN 0x0004
/* Output device. */
#define NFC_IP_IF_OUT 0x0008
/* TOS. */
#define NFC_IP_TOS 0x0010
/* Protocol. */
#define NFC_IP_PROTO 0x0020
/* IP options. */
#define NFC_IP_OPTIONS 0x0040
/* Frag & flags. */
#define NFC_IP_FRAG 0x0080
/* Per-protocol information: only matters if proto match. */
/* TCP flags. */
#define NFC_IP_TCPFLAGS 0x0100
/* Source port. */
#define NFC_IP_SRC_PT 0x0200
/* Dest port. */
#define NFC_IP_DST_PT 0x0400
/* Something else about the proto */
#define NFC_IP_PROTO_UNKNOWN 0x2000
/* IP Hooks */
/* After promisc drops, checksum checks. */
#define NF_IP_PRE_ROUTING 0
/* If the packet is destined for this box. */
#define NF_IP_LOCAL_IN 1
/* If the packet is destined for another interface. */
#define NF_IP_FORWARD 2
/* Packets coming from a local process. */
#define NF_IP_LOCAL_OUT 3
/* Packets about to hit the wire. */
#define NF_IP_POST_ROUTING 4
#define NF_IP_NUMHOOKS 5
#endif /* ! __KERNEL__ */
都包含在#ifndef __KERNEL__中。这样导致以前编译过的模块无法重新编译,因为前面已经声明了__KERNEL__,只能还把#endif挪到前面去。
哪位大侠有研究过这方面的内容?这么做有什么好处吗? |
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