forked from Minki/linux
850db6b8c5
We have a hole in:
[acme@newtoy net-2.6.20]$ pahole net/ipv6/tcp_ipv6.o inet_connection_sock_af_ops
/* /pub/scm/linux/kernel/git/acme/net-2.6.20/include/net/inet_connection_sock.h:38 */
struct inet_connection_sock_af_ops {
int (*queue_xmit)(); /* 0 4 */
void (*send_check)(); /* 4 4 */
int (*rebuild_header)(); /* 8 4 */
int (*conn_request)(); /* 12 4 */
struct sock * (*syn_recv_sock)(); /* 16 4 */
int (*remember_stamp)(); /* 20 4 */
__u16 net_header_len; /* 24 2 */
/* XXX 2 bytes hole, try to pack */
int (*setsockopt)(); /* 28 4 */
int (*getsockopt)(); /* 32 4 */
int (*compat_setsockopt)(); /* 36 4 */
int (*compat_getsockopt)(); /* 40 4 */
void (*addr2sockaddr)(); /* 44 4 */
int sockaddr_len; /* 48 4 */
}; /* size: 52, sum members: 50, holes: 1, sum holes: 2 */
But we don't need sockaddr_len to be an int:
[acme@newtoy net-2.6.20]$ find net -name "*.[ch]" | xargs grep '\.sockaddr_len.\+=' | sort -u
net/dccp/ipv4.c: .sockaddr_len = sizeof(struct sockaddr_in),
net/dccp/ipv6.c: .sockaddr_len = sizeof(struct sockaddr_in6),
net/ipv4/tcp_ipv4.c: .sockaddr_len = sizeof(struct sockaddr_in),
net/ipv6/tcp_ipv6.c: .sockaddr_len = sizeof(struct sockaddr_in6),
net/sctp/ipv6.c: .sockaddr_len = sizeof(struct sockaddr_in6),
net/sctp/protocol.c: .sockaddr_len = sizeof(struct sockaddr_in),
[acme@newtoy net-2.6.20]$ pahole --sizes net/ipv6/tcp_ipv6.o | grep sockaddr_in
struct sockaddr_in: 16 0
struct sockaddr_in6: 28 0
[acme@newtoy net-2.6.20]$
So I turned sockaddr_len a 'u16', and now:
[acme@newtoy net-2.6.20]$ pahole net/ipv6/tcp_ipv6.o inet_connection_sock_af_ops
/* /pub/scm/linux/kernel/git/acme/net-2.6.20/include/net/inet_connection_sock.h:38 */
struct inet_connection_sock_af_ops {
int (*queue_xmit)(); /* 0 4 */
void (*send_check)(); /* 4 4 */
int (*rebuild_header)(); /* 8 4 */
int (*conn_request)(); /* 12 4 */
struct sock * (*syn_recv_sock)(); /* 16 4 */
int (*remember_stamp)(); /* 20 4 */
u16 net_header_len; /* 24 2 */
u16 sockaddr_len; /* 26 2 */
int (*setsockopt)(); /* 28 4 */
int (*getsockopt)(); /* 32 4 */
int (*compat_setsockopt)(); /* 36 4 */
int (*compat_getsockopt)(); /* 40 4 */
void (*addr2sockaddr)(); /* 44 4 */
}; /* size: 48 */
So we've saved 4 bytes:
[acme@newtoy net-2.6.20]$ codiff -sV /tmp/tcp_ipv6.o.before net/ipv6/tcp_ipv6.o
/pub/scm/linux/kernel/git/acme/net-2.6.20/net/ipv6/tcp_ipv6.c:
struct inet_connection_sock_af_ops | -4
net_header_len;
from: __u16 /* 24(0) 2(0) */
to: u16 /* 24(0) 2(0) */
sockaddr_len;
from: int /* 48(0) 4(0) */
to: u16 /* 26(0) 2(0) */
1 struct changed
[acme@newtoy net-2.6.20]$
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
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