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-rw-r--r--Documentation/networking/ip-sysctl.txt13
-rw-r--r--include/net/protocol.h7
-rw-r--r--net/dccp/ipv4.c1
-rw-r--r--net/ipv4/af_inet.c1
-rw-r--r--net/ipv4/icmp.c28
-rw-r--r--net/sctp/protocol.c1
6 files changed, 45 insertions, 6 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 0d71fa962d8a..c97932c88ea3 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -26,7 +26,18 @@ ip_no_pmtu_disc - INTEGER
discarded. Outgoing frames are handled the same as in mode 1,
implicitly setting IP_PMTUDISC_DONT on every created socket.
- Possible values: 0-2
+ Mode 3 is a hardend pmtu discover mode. The kernel will only
+ accept fragmentation-needed errors if the underlying protocol
+ can verify them besides a plain socket lookup. Current
+ protocols for which pmtu events will be honored are TCP, SCTP
+ and DCCP as they verify e.g. the sequence number or the
+ association. This mode should not be enabled globally but is
+ only intended to secure e.g. name servers in namespaces where
+ TCP path mtu must still work but path MTU information of other
+ protocols should be discarded. If enabled globally this mode
+ could break other protocols.
+
+ Possible values: 0-3
Default: FALSE
min_pmtu - INTEGER
diff --git a/include/net/protocol.h b/include/net/protocol.h
index fbf7676c9a02..0e5f8665d7fb 100644
--- a/include/net/protocol.h
+++ b/include/net/protocol.h
@@ -43,7 +43,12 @@ struct net_protocol {
int (*handler)(struct sk_buff *skb);
void (*err_handler)(struct sk_buff *skb, u32 info);
unsigned int no_policy:1,
- netns_ok:1;
+ netns_ok:1,
+ /* does the protocol do more stringent
+ * icmp tag validation than simple
+ * socket lookup?
+ */
+ icmp_strict_tag_validation:1;
};
#if IS_ENABLED(CONFIG_IPV6)
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 88299c29101d..22b5d818b200 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -989,6 +989,7 @@ static const struct net_protocol dccp_v4_protocol = {
.err_handler = dccp_v4_err,
.no_policy = 1,
.netns_ok = 1,
+ .icmp_strict_tag_validation = 1,
};
static const struct proto_ops inet_dccp_ops = {
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 6268a4751e64..ecd2c3f245ce 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1545,6 +1545,7 @@ static const struct net_protocol tcp_protocol = {
.err_handler = tcp_v4_err,
.no_policy = 1,
.netns_ok = 1,
+ .icmp_strict_tag_validation = 1,
};
static const struct net_protocol udp_protocol = {
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index fb3c5637199d..0134663fdbce 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -668,6 +668,16 @@ static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
rcu_read_unlock();
}
+static bool icmp_tag_validation(int proto)
+{
+ bool ok;
+
+ rcu_read_lock();
+ ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
+ rcu_read_unlock();
+ return ok;
+}
+
/*
* Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, ICMP_QUENCH, and
* ICMP_PARAMETERPROB.
@@ -705,12 +715,22 @@ static void icmp_unreach(struct sk_buff *skb)
case ICMP_PORT_UNREACH:
break;
case ICMP_FRAG_NEEDED:
- if (net->ipv4.sysctl_ip_no_pmtu_disc == 2) {
- goto out;
- } else if (net->ipv4.sysctl_ip_no_pmtu_disc) {
+ /* for documentation of the ip_no_pmtu_disc
+ * values please see
+ * Documentation/networking/ip-sysctl.txt
+ */
+ switch (net->ipv4.sysctl_ip_no_pmtu_disc) {
+ default:
LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"),
&iph->daddr);
- } else {
+ break;
+ case 2:
+ goto out;
+ case 3:
+ if (!icmp_tag_validation(iph->protocol))
+ goto out;
+ /* fall through */
+ case 0:
info = ntohs(icmph->un.frag.mtu);
if (!info)
goto out;
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 34b7726bcd7f..7c161084f241 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1030,6 +1030,7 @@ static const struct net_protocol sctp_protocol = {
.err_handler = sctp_v4_err,
.no_policy = 1,
.netns_ok = 1,
+ .icmp_strict_tag_validation = 1,
};
/* IPv4 address related functions. */