From 850db6b8c53ff12eadee9ef2aa69360c06bce057 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 27 Nov 2006 17:56:43 -0200 Subject: [PATCH] [INET_CONNECTION_SOCK]: Pack struct inet_connection_sock_af_ops 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 --- include/net/inet_connection_sock.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index fd3f1d8cdc4a..cccea051e922 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -46,7 +46,8 @@ struct inet_connection_sock_af_ops { struct request_sock *req, struct dst_entry *dst); int (*remember_stamp)(struct sock *sk); - __u16 net_header_len; + u16 net_header_len; + u16 sockaddr_len; int (*setsockopt)(struct sock *sk, int level, int optname, char __user *optval, int optlen); int (*getsockopt)(struct sock *sk, int level, int optname, @@ -58,7 +59,6 @@ struct inet_connection_sock_af_ops { int level, int optname, char __user *optval, int __user *optlen); void (*addr2sockaddr)(struct sock *sk, struct sockaddr *); - int sockaddr_len; }; /** inet_connection_sock - INET connection oriented sock