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linux/net/ipv4/ipvs/ip_vs_xmit.c
Arnaldo Carvalho de Melo 2e07fa9cd3 [SK_BUFF]: Use offsets for skb->{mac,network,transport}_header on 64bit architectures 
With this we save 8 bytes per network packet, leaving a 4 bytes hole to be used
in further shrinking work, likely with the offsetization of other pointers,
such as ->{data,tail,end}, at the cost of adds, that were minimized by the
usual practice of setting skb->{mac,nh,n}.raw to a local variable that is then
accessed multiple times in each function, it also is not more expensive than
before with regards to most of the handling of such headers, like setting one
of these headers to another (transport to network, etc), or subtracting, adding
to/from it, comparing them, etc.

Now we have this layout for sk_buff on a x86_64 machine:

[acme@mica net-2.6.22]$ pahole vmlinux sk_buff
struct sk_buff {
	struct sk_buff *       next;             /*   0   8 */
	struct sk_buff *       prev;             /*   8   8 */
	struct rb_node         rb;               /*  16  24 */
	struct sock *          sk;               /*  40   8 */
	ktime_t                tstamp;           /*  48   8 */
	struct net_device *    dev;              /*  56   8 */
	/* --- cacheline 1 boundary (64 bytes) --- */
	struct net_device *    input_dev;        /*  64   8 */
	sk_buff_data_t         transport_header; /*  72   4 */
	sk_buff_data_t         network_header;   /*  76   4 */
	sk_buff_data_t         mac_header;       /*  80   4 */

	/* XXX 4 bytes hole, try to pack */

	struct dst_entry *     dst;              /*  88   8 */
	struct sec_path *      sp;               /*  96   8 */
	char                   cb[48];           /* 104  48 */
	/* cacheline 2 boundary (128 bytes) was 24 bytes ago*/
	unsigned int           len;              /* 152   4 */
	unsigned int           data_len;         /* 156   4 */
	unsigned int           mac_len;          /* 160   4 */
	union {
		__wsum         csum;             /*       4 */
		__u32          csum_offset;      /*       4 */
	};                                       /* 164   4 */
	__u32                  priority;         /* 168   4 */
	__u8                   local_df:1;       /* 172   1 */
	__u8                   cloned:1;         /* 172   1 */
	__u8                   ip_summed:2;      /* 172   1 */
	__u8                   nohdr:1;          /* 172   1 */
	__u8                   nfctinfo:3;       /* 172   1 */
	__u8                   pkt_type:3;       /* 173   1 */
	__u8                   fclone:2;         /* 173   1 */
	__u8                   ipvs_property:1;  /* 173   1 */

	/* XXX 2 bits hole, try to pack */

	__be16                 protocol;         /* 174   2 */
	void    (*destructor)(struct sk_buff *); /* 176   8 */
	struct nf_conntrack *  nfct;             /* 184   8 */
	/* --- cacheline 3 boundary (192 bytes) --- */
	struct sk_buff *       nfct_reasm;       /* 192   8 */
	struct nf_bridge_info *nf_bridge;        /* 200   8 */
	__u16                  tc_index;         /* 208   2 */
	__u16                  tc_verd;          /* 210   2 */
	dma_cookie_t           dma_cookie;       /* 212   4 */
	__u32                  secmark;          /* 216   4 */
	__u32                  mark;             /* 220   4 */
	unsigned int           truesize;         /* 224   4 */
	atomic_t               users;            /* 228   4 */
	unsigned char *        head;             /* 232   8 */
	unsigned char *        data;             /* 240   8 */
	unsigned char *        tail;             /* 248   8 */
	/* --- cacheline 4 boundary (256 bytes) --- */
	unsigned char *        end;              /* 256   8 */
}; /* size: 264, cachelines: 5 */
   /* sum members: 260, holes: 1, sum holes: 4 */
   /* bit holes: 1, sum bit holes: 2 bits */
   /* last cacheline: 8 bytes */

On 32 bits nothing changes, and pointers continue to be used with the compiler
turning all this abstraction layer into dust. But there are some sk_buff
validation tricks that are now possible, humm... :-)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:26:21 -07:00

564 lines
13 KiB
C
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/*
* ip_vs_xmit.c: various packet transmitters for IPVS
*
* Version: $Id: ip_vs_xmit.c,v 1.2 2002/11/30 01:50:35 wensong Exp $
*
* Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
* Julian Anastasov <ja@ssi.bg>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Changes:
*
*/
#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/tcp.h> /* for tcphdr */
#include <net/tcp.h> /* for csum_tcpudp_magic */
#include <net/udp.h>
#include <net/icmp.h> /* for icmp_send */
#include <net/route.h> /* for ip_route_output */
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <net/ip_vs.h>
/*
* Destination cache to speed up outgoing route lookup
*/
static inline void
__ip_vs_dst_set(struct ip_vs_dest *dest, u32 rtos, struct dst_entry *dst)
{
struct dst_entry *old_dst;
old_dst = dest->dst_cache;
dest->dst_cache = dst;
dest->dst_rtos = rtos;
dst_release(old_dst);
}
static inline struct dst_entry *
__ip_vs_dst_check(struct ip_vs_dest *dest, u32 rtos, u32 cookie)
{
struct dst_entry *dst = dest->dst_cache;
if (!dst)
return NULL;
if ((dst->obsolete || rtos != dest->dst_rtos) &&
dst->ops->check(dst, cookie) == NULL) {
dest->dst_cache = NULL;
dst_release(dst);
return NULL;
}
dst_hold(dst);
return dst;
}
static inline struct rtable *
__ip_vs_get_out_rt(struct ip_vs_conn *cp, u32 rtos)
{
struct rtable *rt; /* Route to the other host */
struct ip_vs_dest *dest = cp->dest;
if (dest) {
spin_lock(&dest->dst_lock);
if (!(rt = (struct rtable *)
__ip_vs_dst_check(dest, rtos, 0))) {
struct flowi fl = {
.oif = 0,
.nl_u = {
.ip4_u = {
.daddr = dest->addr,
.saddr = 0,
.tos = rtos, } },
};
if (ip_route_output_key(&rt, &fl)) {
spin_unlock(&dest->dst_lock);
IP_VS_DBG_RL("ip_route_output error, "
"dest: %u.%u.%u.%u\n",
NIPQUAD(dest->addr));
return NULL;
}
__ip_vs_dst_set(dest, rtos, dst_clone(&rt->u.dst));
IP_VS_DBG(10, "new dst %u.%u.%u.%u, refcnt=%d, rtos=%X\n",
NIPQUAD(dest->addr),
atomic_read(&rt->u.dst.__refcnt), rtos);
}
spin_unlock(&dest->dst_lock);
} else {
struct flowi fl = {
.oif = 0,
.nl_u = {
.ip4_u = {
.daddr = cp->daddr,
.saddr = 0,
.tos = rtos, } },
};
if (ip_route_output_key(&rt, &fl)) {
IP_VS_DBG_RL("ip_route_output error, dest: "
"%u.%u.%u.%u\n", NIPQUAD(cp->daddr));
return NULL;
}
}
return rt;
}
/*
* Release dest->dst_cache before a dest is removed
*/
void
ip_vs_dst_reset(struct ip_vs_dest *dest)
{
struct dst_entry *old_dst;
old_dst = dest->dst_cache;
dest->dst_cache = NULL;
dst_release(old_dst);
}
#define IP_VS_XMIT(skb, rt) \
do { \
(skb)->ipvs_property = 1; \
(skb)->ip_summed = CHECKSUM_NONE; \
NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, (skb), NULL, \
(rt)->u.dst.dev, dst_output); \
} while (0)
/*
* NULL transmitter (do nothing except return NF_ACCEPT)
*/
int
ip_vs_null_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp)
{
/* we do not touch skb and do not need pskb ptr */
return NF_ACCEPT;
}
/*
* Bypass transmitter
* Let packets bypass the destination when the destination is not
* available, it may be only used in transparent cache cluster.
*/
int
ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp)
{
struct rtable *rt; /* Route to the other host */
struct iphdr *iph = ip_hdr(skb);
u8 tos = iph->tos;
int mtu;
struct flowi fl = {
.oif = 0,
.nl_u = {
.ip4_u = {
.daddr = iph->daddr,
.saddr = 0,
.tos = RT_TOS(tos), } },
};
EnterFunction(10);
if (ip_route_output_key(&rt, &fl)) {
IP_VS_DBG_RL("ip_vs_bypass_xmit(): ip_route_output error, "
"dest: %u.%u.%u.%u\n", NIPQUAD(iph->daddr));
goto tx_error_icmp;
}
/* MTU checking */
mtu = dst_mtu(&rt->u.dst);
if ((skb->len > mtu) && (iph->frag_off & htons(IP_DF))) {
ip_rt_put(rt);
icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
IP_VS_DBG_RL("ip_vs_bypass_xmit(): frag needed\n");
goto tx_error;
}
/*
* Call ip_send_check because we are not sure it is called
* after ip_defrag. Is copy-on-write needed?
*/
if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
ip_rt_put(rt);
return NF_STOLEN;
}
ip_send_check(ip_hdr(skb));
/* drop old route */
dst_release(skb->dst);
skb->dst = &rt->u.dst;
/* Another hack: avoid icmp_send in ip_fragment */
skb->local_df = 1;
IP_VS_XMIT(skb, rt);
LeaveFunction(10);
return NF_STOLEN;
tx_error_icmp:
dst_link_failure(skb);
tx_error:
kfree_skb(skb);
LeaveFunction(10);
return NF_STOLEN;
}
/*
* NAT transmitter (only for outside-to-inside nat forwarding)
* Not used for related ICMP
*/
int
ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp)
{
struct rtable *rt; /* Route to the other host */
int mtu;
struct iphdr *iph = ip_hdr(skb);
EnterFunction(10);
/* check if it is a connection of no-client-port */
if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
__be16 _pt, *p;
p = skb_header_pointer(skb, iph->ihl*4, sizeof(_pt), &_pt);
if (p == NULL)
goto tx_error;
ip_vs_conn_fill_cport(cp, *p);
IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
}
if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
goto tx_error_icmp;
/* MTU checking */
mtu = dst_mtu(&rt->u.dst);
if ((skb->len > mtu) && (iph->frag_off & htons(IP_DF))) {
ip_rt_put(rt);
icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
IP_VS_DBG_RL_PKT(0, pp, skb, 0, "ip_vs_nat_xmit(): frag needed for");
goto tx_error;
}
/* copy-on-write the packet before mangling it */
if (!ip_vs_make_skb_writable(&skb, sizeof(struct iphdr)))
goto tx_error_put;
if (skb_cow(skb, rt->u.dst.dev->hard_header_len))
goto tx_error_put;
/* drop old route */
dst_release(skb->dst);
skb->dst = &rt->u.dst;
/* mangle the packet */
if (pp->dnat_handler && !pp->dnat_handler(&skb, pp, cp))
goto tx_error;
ip_hdr(skb)->daddr = cp->daddr;
ip_send_check(ip_hdr(skb));
IP_VS_DBG_PKT(10, pp, skb, 0, "After DNAT");
/* FIXME: when application helper enlarges the packet and the length
is larger than the MTU of outgoing device, there will be still
MTU problem. */
/* Another hack: avoid icmp_send in ip_fragment */
skb->local_df = 1;
IP_VS_XMIT(skb, rt);
LeaveFunction(10);
return NF_STOLEN;
tx_error_icmp:
dst_link_failure(skb);
tx_error:
LeaveFunction(10);
kfree_skb(skb);
return NF_STOLEN;
tx_error_put:
ip_rt_put(rt);
goto tx_error;
}
/*
* IP Tunneling transmitter
*
* This function encapsulates the packet in a new IP packet, its
* destination will be set to cp->daddr. Most code of this function
* is taken from ipip.c.
*
* It is used in VS/TUN cluster. The load balancer selects a real
* server from a cluster based on a scheduling algorithm,
* encapsulates the request packet and forwards it to the selected
* server. For example, all real servers are configured with
* "ifconfig tunl0 <Virtual IP Address> up". When the server receives
* the encapsulated packet, it will decapsulate the packet, processe
* the request and return the response packets directly to the client
* without passing the load balancer. This can greatly increase the
* scalability of virtual server.
*
* Used for ANY protocol
*/
int
ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp)
{
struct rtable *rt; /* Route to the other host */
struct net_device *tdev; /* Device to other host */
struct iphdr *old_iph = ip_hdr(skb);
u8 tos = old_iph->tos;
__be16 df = old_iph->frag_off;
sk_buff_data_t old_transport_header = skb->transport_header;
struct iphdr *iph; /* Our new IP header */
int max_headroom; /* The extra header space needed */
int mtu;
EnterFunction(10);
if (skb->protocol != htons(ETH_P_IP)) {
IP_VS_DBG_RL("ip_vs_tunnel_xmit(): protocol error, "
"ETH_P_IP: %d, skb protocol: %d\n",
htons(ETH_P_IP), skb->protocol);
goto tx_error;
}
if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(tos))))
goto tx_error_icmp;
tdev = rt->u.dst.dev;
mtu = dst_mtu(&rt->u.dst) - sizeof(struct iphdr);
if (mtu < 68) {
ip_rt_put(rt);
IP_VS_DBG_RL("ip_vs_tunnel_xmit(): mtu less than 68\n");
goto tx_error;
}
if (skb->dst)
skb->dst->ops->update_pmtu(skb->dst, mtu);
df |= (old_iph->frag_off & htons(IP_DF));
if ((old_iph->frag_off & htons(IP_DF))
&& mtu < ntohs(old_iph->tot_len)) {
icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
ip_rt_put(rt);
IP_VS_DBG_RL("ip_vs_tunnel_xmit(): frag needed\n");
goto tx_error;
}
/*
* Okay, now see if we can stuff it in the buffer as-is.
*/
max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);
if (skb_headroom(skb) < max_headroom
|| skb_cloned(skb) || skb_shared(skb)) {
struct sk_buff *new_skb =
skb_realloc_headroom(skb, max_headroom);
if (!new_skb) {
ip_rt_put(rt);
kfree_skb(skb);
IP_VS_ERR_RL("ip_vs_tunnel_xmit(): no memory\n");
return NF_STOLEN;
}
kfree_skb(skb);
skb = new_skb;
old_iph = ip_hdr(skb);
}
skb->transport_header = old_transport_header;
/* fix old IP header checksum */
ip_send_check(old_iph);
skb_push(skb, sizeof(struct iphdr));
skb_reset_network_header(skb);
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
/* drop old route */
dst_release(skb->dst);
skb->dst = &rt->u.dst;
/*
* Push down and install the IPIP header.
*/
iph = ip_hdr(skb);
iph->version = 4;
iph->ihl = sizeof(struct iphdr)>>2;
iph->frag_off = df;
iph->protocol = IPPROTO_IPIP;
iph->tos = tos;
iph->daddr = rt->rt_dst;
iph->saddr = rt->rt_src;
iph->ttl = old_iph->ttl;
iph->tot_len = htons(skb->len);
ip_select_ident(iph, &rt->u.dst, NULL);
ip_send_check(iph);
/* Another hack: avoid icmp_send in ip_fragment */
skb->local_df = 1;
IP_VS_XMIT(skb, rt);
LeaveFunction(10);
return NF_STOLEN;
tx_error_icmp:
dst_link_failure(skb);
tx_error:
kfree_skb(skb);
LeaveFunction(10);
return NF_STOLEN;
}
/*
* Direct Routing transmitter
* Used for ANY protocol
*/
int
ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp)
{
struct rtable *rt; /* Route to the other host */
struct iphdr *iph = ip_hdr(skb);
int mtu;
EnterFunction(10);
if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
goto tx_error_icmp;
/* MTU checking */
mtu = dst_mtu(&rt->u.dst);
if ((iph->frag_off & htons(IP_DF)) && skb->len > mtu) {
icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
ip_rt_put(rt);
IP_VS_DBG_RL("ip_vs_dr_xmit(): frag needed\n");
goto tx_error;
}
/*
* Call ip_send_check because we are not sure it is called
* after ip_defrag. Is copy-on-write needed?
*/
if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
ip_rt_put(rt);
return NF_STOLEN;
}
ip_send_check(ip_hdr(skb));
/* drop old route */
dst_release(skb->dst);
skb->dst = &rt->u.dst;
/* Another hack: avoid icmp_send in ip_fragment */
skb->local_df = 1;
IP_VS_XMIT(skb, rt);
LeaveFunction(10);
return NF_STOLEN;
tx_error_icmp:
dst_link_failure(skb);
tx_error:
kfree_skb(skb);
LeaveFunction(10);
return NF_STOLEN;
}
/*
* ICMP packet transmitter
* called by the ip_vs_in_icmp
*/
int
ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp, int offset)
{
struct rtable *rt; /* Route to the other host */
int mtu;
int rc;
EnterFunction(10);
/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
forwarded directly here, because there is no need to
translate address/port back */
if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
if (cp->packet_xmit)
rc = cp->packet_xmit(skb, cp, pp);
else
rc = NF_ACCEPT;
/* do not touch skb anymore */
atomic_inc(&cp->in_pkts);
goto out;
}
/*
* mangle and send the packet here (only for VS/NAT)
*/
if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(ip_hdr(skb)->tos))))
goto tx_error_icmp;
/* MTU checking */
mtu = dst_mtu(&rt->u.dst);
if ((skb->len > mtu) && (ip_hdr(skb)->frag_off & htons(IP_DF))) {
ip_rt_put(rt);
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
IP_VS_DBG_RL("ip_vs_in_icmp(): frag needed\n");
goto tx_error;
}
/* copy-on-write the packet before mangling it */
if (!ip_vs_make_skb_writable(&skb, offset))
goto tx_error_put;
if (skb_cow(skb, rt->u.dst.dev->hard_header_len))
goto tx_error_put;
/* drop the old route when skb is not shared */
dst_release(skb->dst);
skb->dst = &rt->u.dst;
ip_vs_nat_icmp(skb, pp, cp, 0);
/* Another hack: avoid icmp_send in ip_fragment */
skb->local_df = 1;
IP_VS_XMIT(skb, rt);
rc = NF_STOLEN;
goto out;
tx_error_icmp:
dst_link_failure(skb);
tx_error:
dev_kfree_skb(skb);
rc = NF_STOLEN;
out:
LeaveFunction(10);
return rc;
tx_error_put:
ip_rt_put(rt);
goto tx_error;
}
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