From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org,
pabeni@redhat.com, edumazet@google.com, fw@strlen.de,
horms@kernel.org
Subject: [PATCH net 11/13] ipvs: do not mangle ICMP replies for non-first fragments
Date: Thu, 23 Jul 2026 18:39:08 +0200 [thread overview]
Message-ID: <20260723163910.274695-12-pablo@netfilter.org> (raw)
In-Reply-To: <20260723163910.274695-1-pablo@netfilter.org>
From: Julian Anastasov <ja@ssi.bg>
Sashiko warns that ip_vs_nat_icmp() unconditionally mangles the
payload for embedded non-first IPv4 fragments. The problem is
in the very old inverted pp->dont_defrag check which should not
continue when embedded is a non-first TCP/UDP/SCTP fragment.
Check for embedded non-first fragment is also missing from
ip_vs_out_icmp_v6(), it is needed before any connection
lookups that expect ports after the network headers.
Drop the blocking code from ip_vs_in_icmp_v6() which prevents
ICMPv6 from local clients to use non-MASQ forwarding.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Link: https://sashiko.dev/#/patchset/20260720201122.79882-1-ja%40ssi.bg
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
include/net/ip_vs.h | 11 +++---
net/netfilter/ipvs/ip_vs_core.c | 61 ++++++++++++---------------------
net/netfilter/ipvs/ip_vs_xmit.c | 28 +++++++++++----
3 files changed, 48 insertions(+), 52 deletions(-)
diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 4a10a01d6e2f..e6ca930a3507 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -1975,8 +1975,7 @@ int ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp, struct ip_vs_iphdr *iph);
int ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp, unsigned int toff,
- unsigned int wlen, unsigned int hooknum,
- struct ip_vs_iphdr *ciph);
+ unsigned int hooknum, struct ip_vs_iphdr *ciph);
void ip_vs_dest_dst_rcu_free(struct rcu_head *head);
#ifdef CONFIG_IP_VS_IPV6
@@ -1990,8 +1989,7 @@ int ip_vs_dr_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp, struct ip_vs_iphdr *iph);
int ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp, unsigned int toff,
- unsigned int wlen, unsigned int hooknum,
- struct ip_vs_iphdr *ciph);
+ unsigned int hooknum, struct ip_vs_iphdr *ciph);
#endif
#ifdef CONFIG_SYSCTL
@@ -2063,12 +2061,13 @@ static inline bool ip_vs_conn_use_hash2(struct ip_vs_conn *cp)
}
void ip_vs_nat_icmp(struct sk_buff *skb, struct ip_vs_protocol *pp,
- struct ip_vs_conn *cp, int dir, unsigned int toff);
+ struct ip_vs_conn *cp, int dir, unsigned int toff,
+ bool has_ports);
#ifdef CONFIG_IP_VS_IPV6
void ip_vs_nat_icmp_v6(struct sk_buff *skb, struct ip_vs_protocol *pp,
struct ip_vs_conn *cp, int dir, unsigned int toff,
- struct ip_vs_iphdr *ciph);
+ bool has_ports, struct ip_vs_iphdr *ciph);
#endif
static inline __wsum ip_vs_check_diff4(__be32 old, __be32 new, __wsum oldsum)
diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index cd5eb71543ec..7efa209a517b 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -924,7 +924,8 @@ static int ip_vs_route_me_harder(struct netns_ipvs *ipvs, int af,
* - inout: 1=in->out, 0=out->in
*/
void ip_vs_nat_icmp(struct sk_buff *skb, struct ip_vs_protocol *pp,
- struct ip_vs_conn *cp, int inout, unsigned int toff)
+ struct ip_vs_conn *cp, int inout, unsigned int toff,
+ bool has_ports)
{
struct iphdr *iph = ip_hdr(skb);
struct icmphdr *icmph = (struct icmphdr *)(skb->data + toff);
@@ -944,8 +945,7 @@ void ip_vs_nat_icmp(struct sk_buff *skb, struct ip_vs_protocol *pp,
}
/* the TCP/UDP/SCTP port */
- if (IPPROTO_TCP == ciph->protocol || IPPROTO_UDP == ciph->protocol ||
- IPPROTO_SCTP == ciph->protocol) {
+ if (has_ports) {
__be16 *ports = (void *)ciph + ciph->ihl*4;
if (inout)
@@ -970,18 +970,15 @@ void ip_vs_nat_icmp(struct sk_buff *skb, struct ip_vs_protocol *pp,
#ifdef CONFIG_IP_VS_IPV6
void ip_vs_nat_icmp_v6(struct sk_buff *skb, struct ip_vs_protocol *pp,
struct ip_vs_conn *cp, int inout, unsigned int toff,
- struct ip_vs_iphdr *ciph)
+ bool has_ports, struct ip_vs_iphdr *ciph)
{
struct ipv6hdr *iph = ipv6_hdr(skb);
- int protocol;
struct icmp6hdr *icmph;
struct ipv6hdr *cih;
icmph = (struct icmp6hdr *)(skb->data + toff);
cih = (struct ipv6hdr *)(skb->data + ciph->off);
- protocol = ciph->protocol;
-
if (inout) {
iph->saddr = cp->vaddr.in6;
cih->daddr = cp->vaddr.in6;
@@ -991,9 +988,7 @@ void ip_vs_nat_icmp_v6(struct sk_buff *skb, struct ip_vs_protocol *pp,
}
/* the TCP/UDP/SCTP port */
- if (!ciph->fragoffs &&
- (protocol == IPPROTO_TCP || protocol == IPPROTO_UDP ||
- protocol == IPPROTO_SCTP)) {
+ if (has_ports) {
__be16 *ports = (void *)(skb->data + ciph->len);
IP_VS_DBG(11, "%s() changed port %d to %d\n", __func__,
@@ -1035,6 +1030,7 @@ static int handle_response_icmp(int af, struct sk_buff *skb,
int iproto = af == AF_INET6 ? IPPROTO_ICMPV6 : IPPROTO_ICMP;
unsigned int verdict = NF_DROP;
unsigned int ctoff = ciph->len;
+ bool has_ports = false;
if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)
goto after_nat;
@@ -1048,17 +1044,19 @@ static int handle_response_icmp(int af, struct sk_buff *skb,
}
if (ciph->protocol == IPPROTO_TCP || ciph->protocol == IPPROTO_UDP ||
- ciph->protocol == IPPROTO_SCTP)
+ ciph->protocol == IPPROTO_SCTP) {
ctoff += 2 * sizeof(__u16);
+ has_ports = true;
+ }
if (skb_ensure_writable(skb, ctoff))
goto out;
#ifdef CONFIG_IP_VS_IPV6
if (af == AF_INET6)
- ip_vs_nat_icmp_v6(skb, pp, cp, 1, toff, ciph);
+ ip_vs_nat_icmp_v6(skb, pp, cp, 1, toff, has_ports, ciph);
else
#endif
- ip_vs_nat_icmp(skb, pp, cp, 1, toff);
+ ip_vs_nat_icmp(skb, pp, cp, 1, toff, has_ports);
if (ip_vs_route_me_harder(cp->ipvs, af, skb, hooknum))
goto out;
@@ -1142,8 +1140,7 @@ static int ip_vs_out_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb,
return NF_ACCEPT;
/* Is the embedded protocol header present? */
- if (unlikely(cih->frag_off & htons(IP_OFFSET) &&
- pp->dont_defrag))
+ if (unlikely(cih->frag_off & htons(IP_OFFSET) && !pp->dont_defrag))
return NF_ACCEPT;
IP_VS_DBG_PKT(11, AF_INET, pp, skb, offset,
@@ -1207,6 +1204,10 @@ static int ip_vs_out_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,
if (!pp)
return NF_ACCEPT;
+ /* Is the embedded protocol header present? */
+ if (unlikely(ciph.fragoffs && !pp->dont_defrag))
+ return NF_ACCEPT;
+
/* The embedded headers contain source and dest in reverse order */
cp = INDIRECT_CALL_1(pp->conn_out_get, ip_vs_conn_out_get_proto,
ipvs, AF_INET6, skb, &ciph);
@@ -1865,8 +1866,7 @@ ip_vs_in_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb, int *related,
pp = pd->pp;
/* Is the embedded protocol header present? */
- if (unlikely(cih->frag_off & htons(IP_OFFSET) &&
- pp->dont_defrag))
+ if (unlikely(cih->frag_off & htons(IP_OFFSET) && !pp->dont_defrag))
return NF_ACCEPT;
IP_VS_DBG_PKT(11, AF_INET, pp, skb, offset,
@@ -1874,7 +1874,6 @@ ip_vs_in_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb, int *related,
offset2 = offset;
ip_vs_fill_iph_skb_icmp(AF_INET, skb, offset, !tunnel, &ciph);
- offset = ciph.len;
/* The embedded headers contain source and dest in reverse order.
* For IPIP/UDP/GRE tunnel this is error for request, not for reply.
@@ -1968,11 +1967,7 @@ ip_vs_in_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb, int *related,
/* do the statistics and put it back */
ip_vs_in_stats(cp, skb);
- if (IPPROTO_TCP == cih->protocol || IPPROTO_UDP == cih->protocol ||
- IPPROTO_SCTP == cih->protocol)
- offset += 2 * sizeof(__u16);
- verdict = ip_vs_icmp_xmit(skb, cp, pp, iph->len, offset, hooknum,
- &ciph);
+ verdict = ip_vs_icmp_xmit(skb, cp, pp, iph->len, hooknum, &ciph);
out:
if (likely(!new_cp))
@@ -2032,8 +2027,8 @@ static int ip_vs_in_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,
return NF_ACCEPT;
pp = pd->pp;
- /* Cannot handle fragmented embedded protocol */
- if (ciph.fragoffs)
+ /* Is the embedded protocol header present? */
+ if (ciph.fragoffs && !pp->dont_defrag)
return NF_ACCEPT;
IP_VS_DBG_PKT(11, AF_INET6, pp, skb, offset,
@@ -2057,13 +2052,6 @@ static int ip_vs_in_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,
new_cp = true;
}
- /* VS/TUN, VS/DR and LOCALNODE just let it go */
- if ((hooknum == NF_INET_LOCAL_OUT) &&
- (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)) {
- verdict = NF_ACCEPT;
- goto out;
- }
-
verdict = NF_DROP;
/* Ensure the checksum is correct */
@@ -2079,14 +2067,7 @@ static int ip_vs_in_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,
/* do the statistics and put it back */
ip_vs_in_stats(cp, skb);
- /* Need to mangle contained IPv6 header in ICMPv6 packet */
- offset = ciph.len;
- if (IPPROTO_TCP == ciph.protocol || IPPROTO_UDP == ciph.protocol ||
- IPPROTO_SCTP == ciph.protocol)
- offset += 2 * sizeof(__u16); /* Also mangle ports */
-
- verdict = ip_vs_icmp_xmit_v6(skb, cp, pp, iph->len, offset, hooknum,
- &ciph);
+ verdict = ip_vs_icmp_xmit_v6(skb, cp, pp, iph->len, hooknum, &ciph);
out:
if (likely(!new_cp))
diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
index c23401c789de..0b0c5304993a 100644
--- a/net/netfilter/ipvs/ip_vs_xmit.c
+++ b/net/netfilter/ipvs/ip_vs_xmit.c
@@ -1503,13 +1503,14 @@ ip_vs_dr_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
int
ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp, unsigned int toff,
- unsigned int wlen, unsigned int hooknum,
- struct ip_vs_iphdr *ciph)
+ unsigned int hooknum, struct ip_vs_iphdr *ciph)
{
struct rtable *rt; /* Route to the other host */
int rc;
int local;
int rt_mode, was_input;
+ bool has_ports = false;
+ unsigned int wlen;
/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
forwarded directly here, because there is no need to
@@ -1565,6 +1566,13 @@ ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
goto tx_error;
}
+ wlen = ciph->len;
+ if (ciph->protocol == IPPROTO_TCP || ciph->protocol == IPPROTO_UDP ||
+ ciph->protocol == IPPROTO_SCTP) {
+ wlen += 2 * sizeof(__u16); /* Also mangle ports */
+ has_ports = true;
+ }
+
/* copy-on-write the packet before mangling it */
if (skb_ensure_writable(skb, wlen))
goto tx_error;
@@ -1572,7 +1580,7 @@ ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
if (skb_cow(skb, rt->dst.dev->hard_header_len))
goto tx_error;
- ip_vs_nat_icmp(skb, pp, cp, 0, toff);
+ ip_vs_nat_icmp(skb, pp, cp, 0, toff, has_ports);
/* Another hack: avoid icmp_send in ip_fragment */
skb->ignore_df = 1;
@@ -1589,10 +1597,11 @@ ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
int
ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp, unsigned int toff,
- unsigned int wlen, unsigned int hooknum,
- struct ip_vs_iphdr *ciph)
+ unsigned int hooknum, struct ip_vs_iphdr *ciph)
{
+ bool has_ports = false;
struct rt6_info *rt; /* Route to the other host */
+ unsigned int wlen;
int rc;
int local;
int rt_mode;
@@ -1650,6 +1659,13 @@ ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
goto tx_error;
}
+ wlen = ciph->len;
+ if (ciph->protocol == IPPROTO_TCP || ciph->protocol == IPPROTO_UDP ||
+ ciph->protocol == IPPROTO_SCTP) {
+ wlen += 2 * sizeof(__u16); /* Also mangle ports */
+ has_ports = true;
+ }
+
/* copy-on-write the packet before mangling it */
if (skb_ensure_writable(skb, wlen))
goto tx_error;
@@ -1657,7 +1673,7 @@ ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
if (skb_cow(skb, rt->dst.dev->hard_header_len))
goto tx_error;
- ip_vs_nat_icmp_v6(skb, pp, cp, 0, toff, ciph);
+ ip_vs_nat_icmp_v6(skb, pp, cp, 0, toff, has_ports, ciph);
/* Another hack: avoid icmp_send in ip_fragment */
skb->ignore_df = 1;
--
2.47.3
next prev parent reply other threads:[~2026-07-23 16:39 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-23 16:38 [PATCH net,v2 00/13] Netfilter/IPVS fixes for net Pablo Neira Ayuso
2026-07-23 16:38 ` [PATCH net 01/13] netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp() Pablo Neira Ayuso
2026-07-23 16:38 ` [PATCH net 02/13] selftests: netfilter: nft_flowtable.sh: fix offload counter verification for tunnel tests Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 03/13] netfilter: nf_conntrack_expect: add and use nf_ct_expect_related_pair() Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 04/13] netfilter: ipset: do not update comments from kernel-side hash adds Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 05/13] ipvs: do not propagate one-packet flag to synced conns Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 06/13] ipvs: adjust double hashing when fwd method changes Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 07/13] netfilter: nf_tables: make nft_object rhltable per table Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 08/13] netfilter: xt_hashlimit: validate hashtable supports XT_HASHLIMIT_RATE_MATCH Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 09/13] ipvs: fix the checksum validations Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 10/13] ipvs: fix places with wrong packet offsets Pablo Neira Ayuso
2026-07-23 16:39 ` Pablo Neira Ayuso [this message]
2026-07-23 16:39 ` [PATCH net 12/13] ipvs: clear the nfct flag under lock Pablo Neira Ayuso
2026-07-23 16:39 ` [PATCH net 13/13] netfilter: nft_payload: fix mask build for partial field offload Pablo Neira Ayuso
-- strict thread matches above, loose matches on Subject: below --
2026-07-22 21:14 [PATCH net 00/13] Netfilter/IPVS fixes for net Pablo Neira Ayuso
2026-07-22 21:14 ` [PATCH net 11/13] ipvs: do not mangle ICMP replies for non-first fragments Pablo Neira Ayuso
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260723163910.274695-12-pablo@netfilter.org \
--to=pablo@netfilter.org \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=fw@strlen.de \
--cc=horms@kernel.org \
--cc=kuba@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=netfilter-devel@vger.kernel.org \
--cc=pabeni@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.