Simon,
looking at dhcp.c as of this commit, and I see it's unchanged from v2.91:
commit ee09f0655c0a4347a72d2bf9b7231ff158a13f53 (HEAD-> master,
origin/master, origin/HEAD)
Author: Simon Kelley <[email protected]>
Date: Mon Sep 1 22:35:02 2025 +0100
Optimise tftp.
I wonder if the if() clause (next to last line below) is correct, or is
in the right place.
That's currently line #699.
The concern is that everything in the
if(taddr.s_addr==context->router.s_addr)
expression is independent from tmp in the enlosing for(;;) loop, and I
cannot fathom how this would make sense.
I suppose a reasonable compiler can decide the first for(tmp=context;
tmp; tmp=tmp->current) does not cause observable effects (unless
undefined behavior) and just discard the for loop.
Either we want to look at just the context->router.s_addr, then we don't
need the for(),
or the if() clause needs to look at something with "tmp"
to make sense for both lines.
Also, I am confused reading the undocumented fields of struct
dhcp_context {} without reading more than the declaration - it has one
"current" and one "next" pointer and we iterate through "current", which
isn't very typical from just reading it, but done in many places inside
the code so I presume the pointer fields are only named confusingly, so
I cannot assess what impact this inconsistency has.
structdhcp_context*address_available(structdhcp_context*context,
structin_addrtaddr,
structdhcp_netid*netids)
{
/* Check is an address is OK for this network, check all
possible ranges. Make sure that the address isn't in use
by the server itself. */
unsignedintstart, end, addr=ntohl(taddr.s_addr);
structdhcp_context*tmp;
for(tmp=context; tmp; tmp=tmp->current)
if(taddr.s_addr==context->router.s_addr) // <- QUESTIONABLE for/if
VARIABLE CONCORD
returnNULL;
for(tmp=context; tmp; tmp=tmp->current)
{
start=ntohl(tmp->start.s_addr);
end=ntohl(tmp->end.s_addr);
if(!(tmp->flags&(CONTEXT_STATIC|CONTEXT_PROXY)) &&
addr>=start&&
addr<=end&&
match_netid(tmp->filter, netids, 1))
returntmp;
}
returnNULL;
}
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