[gnunet-scheme] 90/324: icmp: Define some packet types and error codes.

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maxime-devos pushed a commit to branch master
in repository gnunet-scheme.

commit 22c3902c579d830027a6823816102482bd067ff1
Author: Maxime Devos <maximedevos@telenet.be>
AuthorDate: Sun Mar 14 15:11:18 2021 +0100

    icmp: Define some packet types and error codes.
    
    One of the underlying transports that GNUnet uses
    is UDP, in which case IIUC the IP_RECVERR option
    can be set on a socket on Linux to receive more
    errors more detailled than errno.
    
    These errors could then be used for more detailed
    error messages.
---
 Makefile.am                |   2 +
 README.org                 |   7 ++
 gnu/gnunet/icmp/struct.scm | 173 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 182 insertions(+)

diff --git a/Makefile.am b/Makefile.am
index d9ecc91..98d624e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -47,6 +47,8 @@ modules = \
   gnu/gnunet/utils/hat-let.scm \
   gnu/gnunet/utils/netstruct.scm \
   \
+  gnu/gnunet/icmp/struct.scm \
+  \
   gnu/gnunet/util/struct.scm \
   gnu/gnunet/crypto/struct.scm \
   gnu/gnunet/hashcode/struct.scm \
diff --git a/README.org b/README.org
index 309f957..0df441e 100644
--- a/README.org
+++ b/README.org
@@ -108,6 +108,13 @@
    + gnu/gnunet/hashcode/struct.scm: hashes
    + gnu/gnunet/crypto/struct.scm: signatures, keys, nonces ...
    + gnu/gnunet/util/struct.scm: various things
+** More refined IP, TCP, UDP, ...
+   + gnu/gnunet/icmp/struct.scm: ICM packet types & codes
+     (incomplete, to be used for error messages)
+
+   TODO: IP_PKTINFO for interface address, scope ...
+   TODO: message queue based upon this
+   TODO: nice abstraction for network errors
 * Conventions
 ** Fibers, capabilities and ambient authority
    Modules are expected to use ‘fibers’ for concurrency.
diff --git a/gnu/gnunet/icmp/struct.scm b/gnu/gnunet/icmp/struct.scm
new file mode 100644
index 0000000..2a206d3
--- /dev/null
+++ b/gnu/gnunet/icmp/struct.scm
@@ -0,0 +1,173 @@
+;; This file is part of scheme-GNUnet.
+;; Copyright (C) 2021 Maxime Devos
+;;
+;; scheme-GNUnet is free software: you can redistribute it and/or modify it
+;; under the terms of the GNU Affero General Public License as published
+;; by the Free Software Foundation, either version 3 of the License,
+;; or (at your option) any later version.
+;;
+;; scheme-GNUnet is distributed in the hope that it will be useful, but
+;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;; Affero General Public License for more details.
+;;
+;; You should have received a copy of the GNU Affero General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+;;
+;; SPDX-License-Identifier: AGPL3.0-or-later
+
+;; Description from RFC 792:
+;; [...]
+;; ICMP messages are sent in several situations:  for example, when a
+;; datagram cannot reach its destination, when the gateway does not have
+;; the buffering capacity to forward a datagram, and when the gateway
+;; can direct the host to send traffic on a shorter route.
+;; [...]
+
+;; While (scheme-)GNUnet does not interect much with the ICMP
+;; protocol (except VPN, maybe?), understanding ICMP somewhat
+;; can be useful for printing informative error messages.
+;;
+;; (On Linux, IP_RECVERR can be used on some Internet sockets
+;; (but not for SOCK_STREAM) to receive some ICMP errors.)
+
+(define-library (gnu gnunet icmp struct)
+  (export icmp-type
+         icmp-type?
+         icmp-code/destination-unreachable
+         icmp-code/time-exceeded
+         icmp-code/parameter-problem
+         icmp-code/destination-unreachable?
+         icmp-code/time-exceeded?
+         icmp-code/parameter-problem?
+         /icmp/destination-unreachable
+         /icmp/time-exceeded
+         /icmp/parameter-problem)
+  (import (only (gnu extractor enum)
+               define-enumeration value)
+         (only (gnu gnunet netstruct syntactic)
+               define-type structure/packed)
+         (only (gnu gnunet netstruct procedural)
+               u8)
+         (only (rnrs base) begin quote))
+  (begin
+
+    ;; Internet RFC 792
+    (define-enumeration (icmp-type icmp-type?)
+      (#:documentation "Type of ICMP packet")
+      (#:max 256)
+      (#:known
+       (value
+       (symbol icmp:echo-reply)
+       (index 0))
+       (value
+       (symbol icmp:destination-unreachable)
+       (index 3))
+       (value
+       (symbol icmp:source-quench)
+       (index 4))
+       (value
+       (symbol icmp:redirect)
+       (index 5))
+       (value
+       (symbol icmp:echo)
+       (index 8))
+       (value
+       (symbol icmp:time-exceeded)
+       (index 11))
+       (value
+       (symbol icmp:parameter-problem)
+       (index 12))
+       (value
+       (symbol icmp:timestamp)
+       (index 13))
+       (value
+       (symbol icmp:timestamp-reply)
+       (index 14))
+       (value
+       (symbol icmp:information-request)
+       (index 15))
+       (value
+       (symbol icmp:information-reply)
+       (index 16))))
+
+    (define-enumeration (icmp-code/destination-unreachable
+                        icmp-code/destination-unreachable?)
+      (#:documentation "something is unreachable")
+      (#:max 256)
+      (#:known
+       (value
+       (symbol icmp:network-unreachable)
+       (index 0))
+       (value
+       (symbol icmp:host-unreachable)
+       (index 1))
+       (value
+       (symbol icmp:protocol-unreachable)
+       (index 2))
+       (value
+       (symbol icmp:port-unreachable)
+       (index 3))
+       (value
+       (symbol icmp:fragmentation-needed)
+       (index 4))
+       (value
+       (symbol icmp:source-route-failed)
+       (index 5))))
+
+    (define-enumeration (icmp-code/time-exceeded
+                        icmp-code/time-exceeded?)
+      (#:documentation "time-out")
+      (#:max 256)
+      (#:known
+       (value
+       (symbol icmp:ttl-exceeded-in-transit)
+       (index 0))
+       (value
+       (symbol icmp:fragment-reassembly-time-exceeded)
+       (index 1))))
+
+    (define-enumeration (icmp-code/parameter-problem
+                        icmp-code/parameter-problem?)
+      (#:documentation "incorrect datagram headers")
+      (#:max 256)
+      (#:known
+       (value
+       ;; provisional name
+       (symbol icmp:pointer-indicates-the-error)
+       (index 0))))
+    
+
+    (define-type /icmp/destination-unreachable
+      (structure/packed
+       (synopsis "a")
+       (documentation
+       "Followed by the internet header + 64 bits of the datagram data")
+       (field (type u8)
+             (properties '((enum-type icmp-type)
+                           (enum-value icmp:destination-unreachable))))
+       (field (code u8)
+             (properties '((enum-type icmp-code/destination-unreachable))))
+       (field (unused u8))))
+
+    (define-type /icmp/time-exceeded
+      (structure/packed
+       (documentation
+       "Followed by the internet header + 64 bits of the datagram data")
+       (field (type u8)
+             (properties '((enum-type icmp-type)
+                           (enum-value icmp:time-exceeded))))
+       (field (code u8)
+             (properties '((enum-type icmp-code/time-exceeded))))))
+
+    (define-type /icmp/parameter-problem
+      (structure/packed
+       (documentation
+       "Followed by the internet header + 64 bits of the datagram data")
+       (field (type u8)
+             (properties '((enum-type icmp-type)
+                           (enum-value icmp:parameter-problem))))
+       (field (code u8)
+             (properties '((enum-type icmp-code/parameter-problem))))
+       (field (parameter u8)
+             (synopsis "If code is 0, the IP option type"))))))

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