c0037a997

Denys Vlasenko

2026-02-24

SUCCESS Duration: 147s

Subject

netstat,pscan: don't use getservbyport(), it links in a static buffer

No binary (build failed)

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

gcc -Wp,-MD,applets/.usage.d -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer      -Iinclude -Iinclude -o applets/usage applets/usage.c

(log yok)

include/libbb.h+3 -0

@@ -911,6 +911,9 @@ char* xmalloc_sockaddr2hostonly_noport(const struct sockaddr *sa) FAST_FUNC RETU
	/* inet_[ap]ton on steroids */
	char* xmalloc_sockaddr2dotted(const struct sockaddr *sa) FAST_FUNC RETURNS_MALLOC;
	char* xmalloc_sockaddr2dotted_noport(const struct sockaddr *sa) FAST_FUNC RETURNS_MALLOC;
+	// NB: unlike getservbyport, port paramenter is NOT in network order
+	#define getservbyport dont_use_getservbyport_uses_global_buffer
+	char* bb_get_servname_by_port(char *p_etc_services, int port, const char type) FAST_FUNC RETURNS_MALLOC;
	// "old" (ipv4 only) API
	// users: traceroute.c hostname.c - use _list_ of all IPs
	struct hostent xgethostbyname(const char name) FAST_FUNC;

libbb/bb_get_servname_by_port.c+48 -0

@@ -0,0 +1,48 @@
+	/*
+	* 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"
+
+	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 portstr, sp_end;
+	char *end;
+	unsigned portnum;
+
+	sp = skip_whitespace(sp);
+	if (*sp == '#')
+	goto next;
+	sp_end = skip_non_whitespace(sp);
+	portstr = skip_whitespace(sp_end);
+	portnum = bb_strtou(portstr, &end, 10);
+	if (portnum != port \|\| *end != '/')
+	goto next;
+	if (type) {
+	end++;
+	end = is_prefixed_with(end, type);
+	if (!end \|\| !(isspace(end) \|\| end == '\0'))
+	goto next;
+	}
+	return auto_string(xstrndup(sp, sp_end - sp));
+	next:
+	sp = strchrnul(sp, '\n');
+	}
+	return NULL;
+	}

networking/netstat.c+6 -5

@@ -176,6 +176,7 @@ struct globals {
	smallint prg_cache_loaded;
	struct prg_node *prg_hash[PRG_HASH_SIZE];
	#endif
+	char **p_etc_services;
	#if ENABLE_FEATURE_NETSTAT_PRG
	const char *progname_banner;
	#endif
@@ -378,15 +379,15 @@ static void build_ipv4_addr(char* local_addr, struct sockaddr_in* localaddr)

	static const char get_sname(int port, const char proto, int numeric)
	{
-	if (!port)
+	if (port == 0)
	return "*";
	if (!numeric) {
-	struct servent *se = getservbyport(port, proto);
+	const char *se = bb_get_servname_by_port(G.p_etc_services, port, proto);
	if (se)
-	return se->s_name;
+	return se;
	}
	/* hummm, we may return static buffer here!! */
-	return itoa(ntohs(port));
+	return itoa(port);
	}

	static char ip_port_str(struct sockaddr addr, int port, const char *proto, int numeric)
@@ -402,7 +403,7 @@ static char ip_port_str(struct sockaddr addr, int port, const char *proto, int
	if (!host)
	host = xmalloc_sockaddr2dotted_noport(addr);

-	xasprintf_inplace(host, "%s:%s", host, get_sname(htons(port), proto, numeric));
+	xasprintf_inplace(host, "%s:%s", host, get_sname(port, proto, numeric));
	return host;
	}

networking/pscan.c+7 -5

@@ -37,13 +37,13 @@
	#define DERR(...) ((void)0)
	#endif

-	static const char *port_name(unsigned port)
+	static const char port_name(char *p_etc_services, unsigned port)
	{
-	struct servent *server;
+	char *server;

-	server = getservbyport(htons(port), NULL);
+	server = bb_get_servname_by_port(p_etc_services, port, NULL);
	if (server)
-	return server->s_name;
+	return server;
	return "unknown";
	}

@@ -62,6 +62,7 @@ int pscan_main(int argc UNUSED_PARAM, char **argv)
	* Rule of thumb: with min_rtt of N msec, scanning 1000 ports
	* will take N seconds at absolute minimum */
	const char opt_min_rtt = "5"; / -T: default min rtt in msec */
+	char *p_etc_services = NULL;
	const char *result_str;
	len_and_sockaddr *lsap;
	int s;
@@ -152,7 +153,8 @@ int pscan_main(int argc UNUSED_PARAM, char **argv)
	DMSG("out of loop @%u", diff);
	if (result_str)
	printf("%5u" "\t" "tcp" "\t" "%s" "\t" "%s" "\n",
-	port, result_str, port_name(port));
+	port, result_str, port_name(&p_etc_services, port)
+	);

	/* Estimate new rtt - we don't want to wait entire timeout
	* for each port. *4 allows for rise in net delay.