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eba75c587e
Add setsockopt SOL_IP/IP_RECVERR_4884 to return the offset to an
extension struct if present.
ICMP messages may include an extension structure after the original
datagram. RFC 4884 standardized this behavior. It stores the offset
in words to the extension header in u8 icmphdr.un.reserved[1].
The field is valid only for ICMP types destination unreachable, time
exceeded and parameter problem, if length is at least 128 bytes and
entire packet does not exceed 576 bytes.
Return the offset to the start of the extension struct when reading an
ICMP error from the error queue, if it matches the above constraints.
Do not return the raw u8 field. Return the offset from the start of
the user buffer, in bytes. The kernel does not return the network and
transport headers, so subtract those.
Also validate the headers. Return the offset regardless of validation,
as an invalid extension must still not be misinterpreted as part of
the original datagram. Note that !invalid does not imply valid. If
the extension version does not match, no validation can take place,
for instance.
For backward compatibility, make this optional, set by setsockopt
SOL_IP/IP_RECVERR_RFC4884. For API example and feature test, see
github.com/wdebruij/kerneltools/blob/master/tests/recv_icmp_v2.c
For forward compatibility, reserve only setsockopt value 1, leaving
other bits for additional icmp extensions.
Changes
v1->v2:
- convert word offset to byte offset from start of user buffer
- return in ee_data as u8 may be insufficient
- define extension struct and object header structs
- return len only if constraints met
- if returning len, also validate
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
42 lines
1,003 B
C
42 lines
1,003 B
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Definitions for the ICMP protocol.
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*
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* Version: @(#)icmp.h 1.0.3 04/28/93
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*
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* Author: Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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*/
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#ifndef _LINUX_ICMP_H
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#define _LINUX_ICMP_H
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#include <linux/skbuff.h>
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#include <uapi/linux/icmp.h>
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#include <uapi/linux/errqueue.h>
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static inline struct icmphdr *icmp_hdr(const struct sk_buff *skb)
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{
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return (struct icmphdr *)skb_transport_header(skb);
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}
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static inline bool icmp_is_err(int type)
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{
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switch (type) {
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case ICMP_DEST_UNREACH:
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case ICMP_SOURCE_QUENCH:
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case ICMP_REDIRECT:
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case ICMP_TIME_EXCEEDED:
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case ICMP_PARAMETERPROB:
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return true;
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}
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return false;
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}
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void ip_icmp_error_rfc4884(const struct sk_buff *skb,
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struct sock_ee_data_rfc4884 *out);
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#endif /* _LINUX_ICMP_H */
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