Change in osmo-ggsn[master]: Implement ICMP response for inactive IP address.

[pespin]

pespin has posted comments on this change. ( https://gerrit.osmocom.org/c/osmo-ggsn/+/24237 )

Change subject: Implement ICMP response for inactive IP address.
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Patch Set 1: Code-Review-1

(5 comments)

https://gerrit.osmocom.org/c/osmo-ggsn/+/24237/1/ggsn/ggsn.c 
File ggsn/ggsn.c:

https://gerrit.osmocom.org/c/osmo-ggsn/+/24237/1/ggsn/ggsn.c@588 
PS1, Line 588: static uint16_t inet_checksum(void *data, int len) {
We already have a lib/icmpv6.c/h files, so it makes sense to move these helper functions to lib/icmpv4.c/h.
Also have a look at lib/checksum.h in case you can reuse something.


https://gerrit.osmocom.org/c/osmo-ggsn/+/24237/1/ggsn/ggsn.c@611 
PS1, Line 611: static void ipv4_host_unreach(struct tun_t *tun, void *pack, unsigned len)
const void *pack


https://gerrit.osmocom.org/c/osmo-ggsn/+/24237/1/ggsn/ggsn.c@613 
PS1, Line 613: 	char send_buf[sizeof(struct ip) + sizeof(struct icmp) + len];
I'm not sure it's really portable to define stack buffers with variable size. In a general case you could use "alloca()" instead, see "man alloca". In this case I think it makes more sense to use a msgb structure.

You can then construct something similar to existing APi for icmpv6 "icmpv6_prepend_ip6hdr()", which can be used generically to prepend icmpv6 header to different messages.


https://gerrit.osmocom.org/c/osmo-ggsn/+/24237/1/ggsn/ggsn.c@614 
PS1, Line 614: 	len = len - 20;
this deserves an explanation ;)


https://gerrit.osmocom.org/c/osmo-ggsn/+/24237/1/ggsn/ggsn.c@723 
PS1, Line 723: 		if (iph->version != 4)
Since we already have icmpv6.c/h, it may be quick to implement the ipv6 part too.



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Gerrit-Project: osmo-ggsn
Gerrit-Branch: master
Gerrit-Change-Id: Ia2c708feab14bb4cada00b0a90e0cb56d680d1aa
Gerrit-Change-Number: 24237
Gerrit-PatchSet: 1
Gerrit-Owner: keith <keith at rhizomatica.org>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-Comment-Date: Mon, 17 May 2021 11:09:45 +0000
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