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/*
* Utility routines.
*
* Copyright (C) 2026 Denys Vlasenko
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
//kbuild:lib-$(CONFIG_NETSTAT) += bb_get_servname_by_port.o
//kbuild:lib-$(CONFIG_PSCAN) += bb_get_servname_by_port.o
#include "libbb.h"
//Rationale for existing:
//#define getservbyport dont_use_getservbyport_uses_global_buffer
//(for example: -280 bytes on musl, x86-32)
char* FAST_FUNC bb_get_servname_by_port(char **p_etc_services, int port, const char *type)
{
char *sp;
sp = *p_etc_services;
if (!sp) {
//TODO: we need mmap_entire_file() for this use case!
sp = xmalloc_open_read_close("/etc/services", NULL);
if (!sp)
return NULL;
*p_etc_services = sp;
}
while (*sp) {
const char *pnstr, *sp_end;
char *end;
unsigned n;
sp = skip_whitespace(sp);
if (*sp == '#')
goto next;
sp_end = skip_non_whitespace(sp);
pnstr = skip_whitespace(sp_end);
n = bb_strtou(pnstr, &end, 10);
if (n != port || *end != '/')
goto next;
if (type) {
end++;
end = is_prefixed_with(end, type);
if (!end
|| !(isspace(*end) || *end == '\0'
|| *end == '#') // glibc treats "http 80/tcp#COMMENT" (no space!) as valid
) {
goto next;
}
}
return auto_string(xstrndup(sp, sp_end - sp));
next:
sp = strchrnul(sp, '\n');
}
return NULL;
}
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