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Date: Thu, 28 Jun 2012 03:59:46 -0700 (PDT)
From: David Miller <davem@...emloft.net>
To: netdev@...r.kernel.org
Subject: [PATCH] ipv4: Create and use fib_compute_spec_dst() helper.
The specific destination is the host we direct unicast replies to.
Usually this is the original packet source address, but if we are
responding to a multicast or broadcast packet we have to use something
different.
Specifically we must use the source address we would use if we were to
send a packet to the unicast source of the original packet.
The routing cache precomputes this value, but we want to remove that
precomputation because it creates a hard dependency on the expensive
rpfilter source address validation which we'd like to make cheaper.
There are only three places where this matters:
1) ICMP replies.
2) pktinfo CMSG
3) IP options
Now there will be no real users of rt->rt_spec_dst and we can simply
remove it altogether.
Signed-off-by: David S. Miller <davem@...emloft.net>
---
include/net/ip_fib.h | 1 +
net/ipv4/fib_frontend.c | 29 +++++++++++++++++++++++++++++
net/ipv4/icmp.c | 6 ++++--
net/ipv4/ip_options.c | 22 +++++++++++-----------
net/ipv4/ip_sockglue.c | 7 ++++---
5 files changed, 49 insertions(+), 16 deletions(-)
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 4b347c0..1687b3d 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -230,6 +230,7 @@ extern struct fib_table *fib_get_table(struct net *net, u32 id);
/* Exported by fib_frontend.c */
extern const struct nla_policy rtm_ipv4_policy[];
extern void ip_fib_init(void);
+extern __be32 fib_compute_spec_dst(struct sk_buff *skb);
extern int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
u8 tos, int oif, struct net_device *dev,
__be32 *spec_dst, u32 *itag);
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 3854411..451939b 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -180,6 +180,35 @@ unsigned int inet_dev_addr_type(struct net *net, const struct net_device *dev,
}
EXPORT_SYMBOL(inet_dev_addr_type);
+__be32 fib_compute_spec_dst(struct sk_buff *skb)
+{
+ struct net_device *dev = skb->dev;
+ struct in_device *in_dev;
+ struct fib_result res;
+ struct flowi4 fl4;
+ struct net *net;
+
+ if (skb->pkt_type != PACKET_BROADCAST &&
+ skb->pkt_type != PACKET_MULTICAST)
+ return ip_hdr(skb)->daddr;
+
+ in_dev = __in_dev_get_rcu(dev);
+ BUG_ON(!in_dev);
+ fl4.flowi4_oif = 0;
+ fl4.flowi4_iif = 0;
+ fl4.daddr = ip_hdr(skb)->saddr;
+ fl4.saddr = ip_hdr(skb)->daddr;
+ fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
+ fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
+ fl4.flowi4_mark = IN_DEV_SRC_VMARK(in_dev) ? skb->mark : 0;
+
+ net = dev_net(dev);
+ if (!fib_lookup(net, &fl4, &res))
+ return FIB_RES_PREFSRC(net, res);
+ else
+ return inet_select_addr(dev, 0, RT_SCOPE_UNIVERSE);
+}
+
/* Given (packet source, input interface) and optional (dst, oif, tos):
* - (main) check, that source is valid i.e. not broadcast or our local
* address.
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 49a74cc..4bce5a2 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -95,6 +95,7 @@
#include <net/checksum.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
+#include <net/ip_fib.h>
/*
* Build xmit assembly blocks
@@ -333,7 +334,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
struct flowi4 fl4;
struct sock *sk;
struct inet_sock *inet;
- __be32 daddr;
+ __be32 daddr, saddr;
if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb))
return;
@@ -347,6 +348,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
inet->tos = ip_hdr(skb)->tos;
daddr = ipc.addr = ip_hdr(skb)->saddr;
+ saddr = fib_compute_spec_dst(skb);
ipc.opt = NULL;
ipc.tx_flags = 0;
if (icmp_param->replyopts.opt.opt.optlen) {
@@ -356,7 +358,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
}
memset(&fl4, 0, sizeof(fl4));
fl4.daddr = daddr;
- fl4.saddr = rt->rt_spec_dst;
+ fl4.saddr = saddr;
fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
fl4.flowi4_proto = IPPROTO_ICMP;
security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
index 708b994..766dfe56 100644
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -27,6 +27,7 @@
#include <net/icmp.h>
#include <net/route.h>
#include <net/cipso_ipv4.h>
+#include <net/ip_fib.h>
/*
* Write options to IP header, record destination address to
@@ -104,7 +105,7 @@ int ip_options_echo(struct ip_options *dopt, struct sk_buff *skb)
sptr = skb_network_header(skb);
dptr = dopt->__data;
- daddr = skb_rtable(skb)->rt_spec_dst;
+ daddr = fib_compute_spec_dst(skb);
if (sopt->rr) {
optlen = sptr[sopt->rr+1];
@@ -250,15 +251,14 @@ void ip_options_fragment(struct sk_buff *skb)
int ip_options_compile(struct net *net,
struct ip_options *opt, struct sk_buff *skb)
{
- int l;
- unsigned char *iph;
- unsigned char *optptr;
- int optlen;
+ __be32 spec_dst = (__force __be32) 0;
unsigned char *pp_ptr = NULL;
- struct rtable *rt = NULL;
+ unsigned char *optptr;
+ unsigned char *iph;
+ int optlen, l;
if (skb != NULL) {
- rt = skb_rtable(skb);
+ spec_dst = fib_compute_spec_dst(skb);
optptr = (unsigned char *)&(ip_hdr(skb)[1]);
} else
optptr = opt->__data;
@@ -330,8 +330,8 @@ int ip_options_compile(struct net *net,
pp_ptr = optptr + 2;
goto error;
}
- if (rt) {
- memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
+ if (skb) {
+ memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
opt->is_changed = 1;
}
optptr[2] += 4;
@@ -372,8 +372,8 @@ int ip_options_compile(struct net *net,
goto error;
}
opt->ts = optptr - iph;
- if (rt) {
- memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
+ if (skb) {
+ memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
timeptr = &optptr[optptr[2]+3];
}
opt->ts_needaddr = 1;
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 0d11f23..de29f46 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -40,6 +40,7 @@
#if IS_ENABLED(CONFIG_IPV6)
#include <net/transp_v6.h>
#endif
+#include <net/ip_fib.h>
#include <linux/errqueue.h>
#include <asm/uaccess.h>
@@ -1019,8 +1020,8 @@ e_inval:
* @sk: socket
* @skb: buffer
*
- * To support IP_CMSG_PKTINFO option, we store rt_iif and rt_spec_dst
- * in skb->cb[] before dst drop.
+ * To support IP_CMSG_PKTINFO option, we store rt_iif and specific
+ * destination in skb->cb[] before dst drop.
* This way, receiver doesnt make cache line misses to read rtable.
*/
void ipv4_pktinfo_prepare(struct sk_buff *skb)
@@ -1030,7 +1031,7 @@ void ipv4_pktinfo_prepare(struct sk_buff *skb)
if (rt) {
pktinfo->ipi_ifindex = rt->rt_iif;
- pktinfo->ipi_spec_dst.s_addr = rt->rt_spec_dst;
+ pktinfo->ipi_spec_dst.s_addr = fib_compute_spec_dst(skb);
} else {
pktinfo->ipi_ifindex = 0;
pktinfo->ipi_spec_dst.s_addr = 0;
--
1.7.10.2
--
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