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Message-Id: <20210716002742.31078-3-Cole.Dishington@alliedtelesis.co.nz>
Date: Fri, 16 Jul 2021 12:27:41 +1200
From: Cole Dishington <Cole.Dishington@...iedtelesis.co.nz>
To: pablo@...filter.org
Cc: kadlec@...filter.org, fw@...len.de, davem@...emloft.net,
kuba@...nel.org, shuah@...nel.org, linux-kernel@...r.kernel.org,
netfilter-devel@...r.kernel.org, coreteam@...filter.org,
netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
Cole Dishington <Cole.Dishington@...iedtelesis.co.nz>,
Anthony Lineham <anthony.lineham@...iedtelesis.co.nz>,
Scott Parlane <scott.parlane@...iedtelesis.co.nz>,
Blair Steven <blair.steven@...iedtelesis.co.nz>
Subject: [PATCH 2/3] net: netfilter: Add RFC-7597 Section 5.1 PSID support
Adds support for masquerading into a smaller subset of ports -
defined by the PSID values from RFC-7597 Section 5.1. This is part of
the support for MAP-E and Lightweight 4over6, which allows multiple
devices to share an IPv4 address by splitting the L4 port / id into
ranges.
Co-developed-by: Anthony Lineham <anthony.lineham@...iedtelesis.co.nz>
Signed-off-by: Anthony Lineham <anthony.lineham@...iedtelesis.co.nz>
Co-developed-by: Scott Parlane <scott.parlane@...iedtelesis.co.nz>
Signed-off-by: Scott Parlane <scott.parlane@...iedtelesis.co.nz>
Signed-off-by: Blair Steven <blair.steven@...iedtelesis.co.nz>
Signed-off-by: Cole Dishington <Cole.Dishington@...iedtelesis.co.nz>
---
Notes:
Thanks for your time reviewing!
Changes in v4:
- Add support for a=0 (A=2^16) special case.
- Now that offset=0 is used for the special case of 2^16 (as it cannot fit
in a u16) the divide by zero issues are no longer present.
net/netfilter/nf_nat_core.c | 39 +++++++++++++++++++++++++++----
net/netfilter/nf_nat_masquerade.c | 20 ++++++++++++++--
2 files changed, 53 insertions(+), 6 deletions(-)
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 7de595ead06a..4a9448684504 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -195,13 +195,36 @@ static bool nf_nat_inet_in_range(const struct nf_conntrack_tuple *t,
static bool l4proto_in_range(const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype,
const union nf_conntrack_man_proto *min,
- const union nf_conntrack_man_proto *max)
+ const union nf_conntrack_man_proto *max,
+ const union nf_conntrack_man_proto *base,
+ bool is_psid)
{
__be16 port;
+ u16 psid, psid_mask, offset_mask;
+
+ /* In this case we are in PSID mode, avoid checking all ranges by computing bitmasks */
+ if (is_psid) {
+ u16 power_j = ntohs(max->all) - ntohs(min->all) + 1;
+ u32 offset = ntohs(base->all);
+ u16 power_a;
+
+ if (offset == 0)
+ offset = 1 << 16;
+
+ power_a = (1 << 16) / offset;
+ offset_mask = (power_a - 1) * offset;
+ psid_mask = ((offset / power_j) << 1) - 1;
+ psid = ntohs(min->all) & psid_mask;
+ }
switch (tuple->dst.protonum) {
case IPPROTO_ICMP:
case IPPROTO_ICMPV6:
+ if (is_psid) {
+ return (offset_mask == 0 ||
+ (ntohs(tuple->src.u.icmp.id) & offset_mask) != 0) &&
+ ((ntohs(tuple->src.u.icmp.id) & psid_mask) == psid);
+ }
return ntohs(tuple->src.u.icmp.id) >= ntohs(min->icmp.id) &&
ntohs(tuple->src.u.icmp.id) <= ntohs(max->icmp.id);
case IPPROTO_GRE: /* all fall though */
@@ -215,6 +238,10 @@ static bool l4proto_in_range(const struct nf_conntrack_tuple *tuple,
else
port = tuple->dst.u.all;
+ if (is_psid) {
+ return (offset_mask == 0 || (ntohs(port) & offset_mask) != 0) &&
+ ((ntohs(port) & psid_mask) == psid);
+ }
return ntohs(port) >= ntohs(min->all) &&
ntohs(port) <= ntohs(max->all);
default:
@@ -239,7 +266,8 @@ static int in_range(const struct nf_conntrack_tuple *tuple,
return 1;
return l4proto_in_range(tuple, NF_NAT_MANIP_SRC,
- &range->min_proto, &range->max_proto);
+ &range->min_proto, &range->max_proto, &range->base_proto,
+ range->flags & NF_NAT_RANGE_PSID);
}
static inline int
@@ -532,8 +560,11 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple,
if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
if (!(range->flags & NF_NAT_RANGE_PROTO_OFFSET) &&
l4proto_in_range(tuple, maniptype,
- &range->min_proto,
- &range->max_proto) &&
+ &range->min_proto,
+ &range->max_proto,
+ &range->base_proto,
+ range->flags &
+ NF_NAT_RANGE_PSID) &&
(range->min_proto.all == range->max_proto.all ||
!nf_nat_used_tuple(tuple, ct)))
return;
diff --git a/net/netfilter/nf_nat_masquerade.c b/net/netfilter/nf_nat_masquerade.c
index 8e8a65d46345..7e2fb0da344a 100644
--- a/net/netfilter/nf_nat_masquerade.c
+++ b/net/netfilter/nf_nat_masquerade.c
@@ -55,8 +55,24 @@ nf_nat_masquerade_ipv4(struct sk_buff *skb, unsigned int hooknum,
newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
newrange.min_addr.ip = newsrc;
newrange.max_addr.ip = newsrc;
- newrange.min_proto = range->min_proto;
- newrange.max_proto = range->max_proto;
+
+ if (range->flags & NF_NAT_RANGE_PSID) {
+ u16 base = ntohs(range->base_proto.all);
+ u16 min = ntohs(range->min_proto.all);
+ u16 off = 0;
+
+ /* If offset=0, port range is in one contiguous block */
+ if (base)
+ off = prandom_u32() % (((1 << 16) / base) - 1);
+
+ newrange.min_proto.all = htons(min + base * off);
+ newrange.max_proto.all = htons(ntohs(newrange.min_proto.all) + ntohs(range->max_proto.all) - min);
+ newrange.base_proto = range->base_proto;
+ newrange.flags = newrange.flags | NF_NAT_RANGE_PROTO_SPECIFIED;
+ } else {
+ newrange.min_proto = range->min_proto;
+ newrange.max_proto = range->max_proto;
+ }
/* Hand modified range to generic setup. */
return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
--
2.32.0
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