Resolution differences for getaddrinfo versus host/dig/delv

[Mark Andrews]

Mark Andrews writes:
> 
> Mark Andrews writes:
> > 	
> > And whomever added underscorechar() to that should be shot.  There
> > are good reasons to be able to distingish hostnames from other sorts
> > of text.  Adding '_' doesn't help one do that as it is impossible to
> > distinguish underscored text from underscored hostnames. 
> > 
> > 	This_is_a_title
> 
> Lets try the example again.
> 
> 	_T_h_i_s__i_s__a__t_i_t_l_e

Or even better

	_A_ _q_u_e_s_t_i_o_n_ _a_b_o_u_t_ _e_x_a_m_p_l_e_._c_o_m_.

>  
> > Mark
> > 	
> > In message <20151118212633.GA18852 at sources.org>, Stephane Bortzmeyer writes
> :
> > > On Wed, Nov 18, 2015 at 12:19:57PM +0000,
> > >  Phil Mayers <p.mayers at imperial.ac.uk> wrote
> > >  a message of 44 lines which said:
> > >
> > > > I suspect getaddrinfo isn't parsing the DNS response for some reason.
> > > ...
> > > > Obviously the *.thing on the RHS of the first CNAME is weird, but is it
> > > > illegal?
> > >
> > > Yes, for a *host* name (no for a *domain* name). See Tony Finch's
> > > explanation.
> > >
> > > In the GNU libc, the relevant code is in resolv/res_comp.c and
> > > includes this function, which tests that a *host* name is
> > > a-z0-9\.\-+:
> > >
> > > #define alphachar(c) (((c) >= 0x41 && (c) <= 0x5a) \
> > > 		   || ((c) >= 0x61 && (c) <= 0x7a))
> > > #define digitchar(c) ((c) >= 0x30 && (c) <= 0x39)
> > >
> > > #define borderchar(c) (alphachar(c) || digitchar(c))
> > > #define middlechar(c) (borderchar(c) || hyphenchar(c) ||
> > > underscorechar(c))
> > > #define	domainchar(c) ((c) > 0x20 && (c) < 0x7f)
> > >
> > > int
> > > res_hnok(const char *dn) {
> > > 	int pch = PERIOD, ch = *dn++;
> > >
> > > 	while (ch != '\0') {
> > > 		int nch = *dn++;
> > >
> > > 		if (periodchar(ch)) {
> > > 			(void)NULL;
> > > 		} else if (periodchar(pch)) {
> > > 			if (!borderchar(ch))
> > > 				return (0);
> > > 		} else if (periodchar(nch) || nch == '\0') {
> > > 			if (!borderchar(ch))
> > > 				return (0);
> > > 		} else {
> > > 			if (!middlechar(ch))
> > > 				return (0);
> > > 		}
> > > 		pch = ch, ch = nch;
> > > 	}
> > > 	return (1);
> > > }	
> > > _______________________________________________
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> > 
> > -- 
> > Mark Andrews, ISC
> > 1 Seymour St., Dundas Valley, NSW 2117, Australia
> > PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org
> -- 
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org