From: Ishaan Gandhi <ishaangan...@gmail.com>
This patch identifies the interface a packet arrived on when sending
ICMP time exceeded, destination unreachable, and parameter problem
messages, in accordance with RFC 5837.
It was tested by pinging a machine with a ttl of 1, and observing the
response in Wireshark.
Changes since v1:
- Add sysctls, feature is disabled by default
- Device name is always less than 63, so don't check this
- MTU is always included in net_device, so don't check its presence
- Support IPv6 as first class citizen
- Increment lengths via sizeof operator as opposed to int literals
- Initialize more local variables with defaults
Change request still unaddressed:
- Willem pointed out yesterday that `skb_iif` is not guaranteed
to be the iif of the device the packet arrived on. To get around this
I propose adding a `skb_orig_iif` field to sk_buff which will remain
unchanged after rounds. Would this be ok?
Signed-off-by: Ishaan Gandhi <ishaangan...@gmail.com>
---
Documentation/networking/ip-sysctl.rst | 10 ++
include/linux/icmp.h | 3 +
include/net/netns/ipv4.h | 1 +
include/net/netns/ipv6.h | 1 +
include/uapi/linux/icmp.h | 26 ++++
net/ipv4/icmp.c | 170 +++++++++++++++++++++++++
net/ipv4/sysctl_net_ipv4.c | 7 +
net/ipv6/af_inet6.c | 1 +
net/ipv6/icmp.c | 15 +++
9 files changed, 234 insertions(+)
diff --git a/Documentation/networking/ip-sysctl.rst
b/Documentation/networking/ip-sysctl.rst
index 837d51f9e1fa..a54b0c75ca76 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -1204,6 +1204,16 @@ icmp_errors_use_inbound_ifaddr - BOOLEAN
Default: 0
+icmp_errors_identify_if - BOOLEAN
+
+ If set non-zero, then the kernel will append an extension
+ object identifying the interface on which the packet
+ which caused the error. The object will contain the ifIndex,
+ interface name, interface IP address, and/or MTU, in accordance
+ with RFC5837.
+
+ Default: 0
+
igmp_max_memberships - INTEGER
Change the maximum number of multicast groups we can subscribe to.
Default: 20
diff --git a/include/linux/icmp.h b/include/linux/icmp.h
index 8fc38a34cb20..db1a17dbc338 100644
--- a/include/linux/icmp.h
+++ b/include/linux/icmp.h
@@ -39,4 +39,7 @@ static inline bool icmp_is_err(int type)
void ip_icmp_error_rfc4884(const struct sk_buff *skb,
struct sock_ee_data_rfc4884 *out);
+void icmp_identify_arrival_interface(struct sk_buff *skb, struct net *net, int
room,
+ char *icmph, int ip_version);
+
#endif /* _LINUX_ICMP_H */
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 9e36738c1fe1..fd68a47f1130 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -90,6 +90,7 @@ struct netns_ipv4 {
int sysctl_icmp_ratelimit;
int sysctl_icmp_ratemask;
int sysctl_icmp_errors_use_inbound_ifaddr;
+ int sysctl_icmp_errors_identify_if;
struct local_ports ip_local_ports;
diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 5ec054473d81..9608e0a82401 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -36,6 +36,7 @@ struct netns_sysctl_ipv6 {
int icmpv6_echo_ignore_all;
int icmpv6_echo_ignore_multicast;
int icmpv6_echo_ignore_anycast;
+ int icmpv6_errors_identify_if;
DECLARE_BITMAP(icmpv6_ratemask, ICMPV6_MSG_MAX + 1);
unsigned long *icmpv6_ratemask_ptr;
int anycast_src_echo_reply;
diff --git a/include/uapi/linux/icmp.h b/include/uapi/linux/icmp.h
index fb169a50895e..f43ecd3c3677 100644
--- a/include/uapi/linux/icmp.h
+++ b/include/uapi/linux/icmp.h
@@ -118,4 +118,30 @@ struct icmp_extobj_hdr {
__u8 class_type;
};
+/* RFC 5837 Bitmasks */
+#define ICMP_5837_MTU_CTYPE (1 << 0)
+#define ICMP_5837_NAME_CTYPE (1 << 1)
+#define ICMP_5837_IP_ADDR_CTYPE (1 << 2)
+#define ICMP_5837_IF_INDEX_CTYPE (1 << 3)
+
+#define ICMP_5837_ARRIVAL_ROLE_CTYPE (0 << 6)
+#define ICMP_5837_SUB_IP_ROLE_CTYPE (1 << 6)
+#define ICMP_5837_FORWARD_ROLE_CTYPE (2 << 6)
+#define ICMP_5837_NEXT_HOP_ROLE_CTYPE (3 << 6)
+
+#define ICMP_5837_MIN_ORIG_LEN 128
+
+/* RFC 5837 Interface IP Address sub-object */
+struct interface_ipv4_addr_sub_obj {
+ __be16 afi;
+ __be16 reserved;
+ __be32 addr;
+};
+
+struct interface_ipv6_addr_sub_obj {
+ __be16 afi;
+ __be16 reserved;
+ __be32 addr[4];
+};
+
#endif /* _UAPI_LINUX_ICMP_H */
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 793aebf07c2a..a3a8b028fdcf 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -87,6 +87,7 @@
#include <linux/timer.h>
#include <linux/init.h>
#include <linux/uaccess.h>
+#include <net/addrconf.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
@@ -555,6 +556,169 @@ static struct rtable *icmp_route_lookup(struct net *net,
return ERR_PTR(err);
}
+/* Appends interface identification object to ICMP packet to identify
+ * the interface on which the original datagram arrived, per RFC 5837.
+ *
+ * Should only be called on the following messages
+ * - ICMPv4 Time Exceeded
+ * - ICMPv4 Destination Unreachable
+ * - ICMPv4 Parameter Problem
+ * - ICMPv6 Time Exceeded
+ * - ICMPv6 Destination Unreachable
+ */
+
+void icmp_identify_arrival_interface(struct sk_buff *skb, struct net *net, int
room,
+ char *icmph, int ip_version)
+{
+ unsigned int ext_len, orig_len, word_aligned_orig_len, offset,
extra_space_needed,
+ if_index, mtu = 0, name_len = 0, name_subobj_len = 0;
+ struct interface_ipv4_addr_sub_obj ip4_addr_subobj = {.addr = 0};
+ struct interface_ipv6_addr_sub_obj ip6_addr_subobj;
+ struct icmp_extobj_hdr *iio_hdr;
+ struct inet6_ifaddr ip6_ifaddr;
+ struct inet6_dev *dev6 = NULL;
+ struct icmp_ext_hdr *ext_hdr;
+ char *name = NULL, ctype;
+ struct net_device *dev;
+ void *subobj_offset;
+
+ if (ip_version != 4 && ip_version != 6) {
+ pr_debug("ip_version must be 4 or 6\n");
+ return;
+ }
+ skb_linearize(skb);
+ if_index = inet_iif(skb);
+ orig_len = skb->len - skb_network_offset(skb);
+
+ // IPv4 messages MUST be 32-bit aligned, IPv6 64-bit aligned
+ if (ip_version == 4) {
+ word_aligned_orig_len = (orig_len + 3) & ~0x03;
+ icmph[6] = word_aligned_orig_len / 4;
+ } else {
+ word_aligned_orig_len = (orig_len + 7) & ~0x07;
+ icmph[5] = word_aligned_orig_len / 8;
+ }
+
+ ctype = ICMP_5837_ARRIVAL_ROLE_CTYPE;
+ ext_len = sizeof(struct icmp_ext_hdr) + sizeof(struct icmp_extobj_hdr);
+
+ // Always add if_index to the IIO
+ ext_len += sizeof(__be32);
+ ctype |= ICMP_5837_IF_INDEX_CTYPE;
+
+ dev = dev_get_by_index(net, if_index);
+ // Try to append IP address, name, and MTU
+ if (dev) {
+ if (ip_version == 4) {
+ ip4_addr_subobj.addr = inet_select_addr(dev, 0,
RT_SCOPE_UNIVERSE);
+ if (ip4_addr_subobj.addr) {
+ ip4_addr_subobj.afi = htons(1);
+ ip4_addr_subobj.reserved = 0;
+ ctype |= ICMP_5837_IP_ADDR_CTYPE;
+ ext_len += sizeof(ip4_addr_subobj);
+ }
+ }
+ if (ip_version == 6) {
+ dev6 = in6_dev_get(dev);
+ if (dev6) {
+ ip6_ifaddr = *list_last_entry(&dev6->addr_list,
+ struct
inet6_ifaddr, if_list);
+ memcpy(ip6_addr_subobj.addr,
ip6_ifaddr.addr.s6_addr32,
+ sizeof(ip6_addr_subobj.addr));
+ ip6_addr_subobj.afi = htons(2);
+ ip6_addr_subobj.reserved = 0;
+ ctype |= ICMP_5837_IP_ADDR_CTYPE;
+ ext_len += sizeof(ip6_addr_subobj);
+ }
+ }
+
+ name = dev->name;
+ if (name) {
+ name_len = strlen(name);
+ // 1 extra byte for the length field
+ name_subobj_len = name_len + 1;
+ // Sub-objects must be aligned to 32-bits
+ name_subobj_len = (name_subobj_len + 3) & ~0x03;
+ ctype |= ICMP_5837_NAME_CTYPE;
+ ext_len += name_subobj_len;
+ }
+
+ mtu = dev->mtu;
+ ctype |= ICMP_5837_MTU_CTYPE;
+ ext_len += sizeof(__be32);
+ }
+
+ if (word_aligned_orig_len + ext_len > room) {
+ offset = room - ext_len;
+ extra_space_needed = room - orig_len;
+ } else if (orig_len < ICMP_5837_MIN_ORIG_LEN) {
+ // Original packet must be zero padded to 128 bytes
+ offset = ICMP_5837_MIN_ORIG_LEN;
+ extra_space_needed = offset + ext_len - orig_len;
+ } else {
+ // There is enough room to just add to the end of the packet
+ offset = word_aligned_orig_len;
+ extra_space_needed = ext_len;
+ }
+
+ if (skb_tailroom(skb) < extra_space_needed) {
+ if (pskb_expand_head(skb, 0, extra_space_needed -
skb_tailroom(skb), GFP_ATOMIC))
+ return;
+ }
+
+ // Zero-pad from the end of the original message to the beginning of
the header
+ if (orig_len < ICMP_5837_MIN_ORIG_LEN) {
+ // Original packet must be zero-padded to 128 bytes
+ memset(skb_network_header(skb) + orig_len, 0,
ICMP_5837_MIN_ORIG_LEN - orig_len);
+ } else {
+ // Just zero-pad so the original packet is word aligned
+ memset(skb_network_header(skb) + orig_len, 0,
word_aligned_orig_len - orig_len);
+ }
+
+ skb_put(skb, extra_space_needed);
+ ext_hdr = (struct icmp_ext_hdr *)(skb_network_header(skb) + offset);
+ iio_hdr = (struct icmp_extobj_hdr *)(ext_hdr + 1);
+ subobj_offset = (void *)(iio_hdr + 1);
+
+ ext_hdr->reserved1 = 0;
+ ext_hdr->reserved2 = 0;
+ ext_hdr->version = 2;
+ ext_hdr->checksum = 0;
+
+ iio_hdr->length = htons(ext_len - sizeof(struct icmp_ext_hdr));
+ iio_hdr->class_num = 2;
+ iio_hdr->class_type = ctype;
+
+ *(__be32 *)subobj_offset = htonl(if_index);
+ subobj_offset += sizeof(__be32);
+
+ if (ip4_addr_subobj.addr) {
+ *(struct interface_ipv4_addr_sub_obj *)subobj_offset =
ip4_addr_subobj;
+ subobj_offset += sizeof(ip4_addr_subobj);
+ }
+
+ if (dev6) {
+ *(struct interface_ipv6_addr_sub_obj *)subobj_offset =
ip6_addr_subobj;
+ subobj_offset += sizeof(ip6_addr_subobj);
+ }
+
+ if (name) {
+ *(__u8 *)subobj_offset = name_subobj_len;
+ subobj_offset += sizeof(__u8);
+ memcpy(subobj_offset, name, name_len);
+ memset(subobj_offset + name_len, 0, name_subobj_len - (name_len
+ sizeof(__u8)));
+ subobj_offset += name_subobj_len - sizeof(__u8);
+ }
+
+ if (mtu) {
+ *(__be32 *)subobj_offset = htonl(mtu);
+ subobj_offset += sizeof(__be32);
+ }
+
+ ext_hdr->checksum =
+ csum_fold(skb_checksum(skb, skb_network_offset(skb) + offset,
ext_len, 0));
+}
+
/*
* Send an ICMP message in response to a situation
*
@@ -731,6 +895,11 @@ void __icmp_send(struct sk_buff *skb_in, int type, int
code, __be32 info,
room = 576;
room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
room -= sizeof(struct icmphdr);
+ if (net->ipv4.sysctl_icmp_errors_identify_if && (type ==
ICMP_DEST_UNREACH ||
+ type == ICMP_TIME_EXCEEDED || type == ICMP_PARAMETERPROB)) {
+ icmp_identify_arrival_interface(skb_in, net, room,
+ (char *)&icmp_param.data.icmph,
4);
+ }
icmp_param.data_len = skb_in->len - icmp_param.offset;
if (icmp_param.data_len > room)
@@ -1349,6 +1518,7 @@ static int __net_init icmp_sk_init(struct net *net)
net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
net->ipv4.sysctl_icmp_ratemask = 0x1818;
net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
+ net->ipv4.sysctl_icmp_errors_identify_if = 0;
return 0;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 5653e3b011bf..8a2e6ce2e74e 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -628,6 +628,13 @@ static struct ctl_table ipv4_net_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
+ {
+ .procname = "icmp_errors_identify_if",
+ .data = &init_net.ipv4.sysctl_icmp_errors_identify_if,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
{
.procname = "icmp_ratelimit",
.data = &init_net.ipv4.sysctl_icmp_ratelimit,
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index b304b882e031..3901c2a99be4 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -939,6 +939,7 @@ static int __net_init inet6_net_init(struct net *net)
net->ipv6.sysctl.icmpv6_echo_ignore_all = 0;
net->ipv6.sysctl.icmpv6_echo_ignore_multicast = 0;
net->ipv6.sysctl.icmpv6_echo_ignore_anycast = 0;
+ net->ipv6.sysctl.icmpv6_errors_identify_if = 0;
/* By default, rate limit error messages.
* Except for pmtu discovery, it would break it.
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 9df8737ae0d3..f1ae0160cb2b 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -595,6 +595,13 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8
code, __u32 info,
msg.offset = skb_network_offset(skb);
msg.type = type;
+ if (net->ipv6.sysctl.icmpv6_errors_identify_if &&
+ (type == ICMPV6_DEST_UNREACH || type == ICMPV6_TIME_EXCEED)) {
+ icmp_identify_arrival_interface(skb, net,
+ IPV6_MIN_MTU - sizeof(struct ipv6hdr) - sizeof(struct
icmp6hdr),
+ (char *)&tmp_hdr, 6);
+ }
+
len = skb->len - msg.offset;
len = min_t(unsigned int, len, IPV6_MIN_MTU - sizeof(struct ipv6hdr) -
sizeof(struct icmp6hdr));
if (len < 0) {
@@ -1184,6 +1191,13 @@ static struct ctl_table ipv6_icmp_table_template[] = {
.mode = 0644,
.proc_handler = proc_do_large_bitmap,
},
+ {
+ .procname = "errors_identify_if",
+ .data =
&init_net.ipv6.sysctl.icmpv6_errors_identify_if,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
{ },
};
@@ -1201,6 +1215,7 @@ struct ctl_table * __net_init
ipv6_icmp_sysctl_init(struct net *net)
table[2].data = &net->ipv6.sysctl.icmpv6_echo_ignore_multicast;
table[3].data = &net->ipv6.sysctl.icmpv6_echo_ignore_anycast;
table[4].data = &net->ipv6.sysctl.icmpv6_ratemask_ptr;
+ table[5].data = &net->ipv6.sysctl.icmpv6_errors_identify_if;
}
return table;
}
--
2.25.1
