From: Andrew Bower <andrew@bower.uk>
Author: Jun-ichiro itojun Hagino
Origin: https://www.openwall.com/popa3d/contrib/popa3d-0.5.1-ipv6-patch-1.diff.gz
Bug-Debian: https://bugs.debian.org/1040606
Forwarded: https://github.com/openwall/popa3d/pull/3
Last-Update: 2025-08-23
Subject: Patch to support IPv6

Incidentally re-fixes use of reserved word true as variable name.
---
 popa3d.8     |  23 +++++++++++++
 standalone.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
 startup.c    |  17 +++++++++-
 virtual.c    |  29 +++++++++++-----
 4 files changed, 148 insertions(+), 29 deletions(-)

diff --git a/popa3d.8 b/popa3d.8
index d7a0c3d..56a48b9 100644
--- a/popa3d.8
+++ b/popa3d.8
@@ -6,6 +6,8 @@ popa3d \- Post Office Protocol (POP3) server
 .RB [ -D ]
 .RB [ -F ]
 .RB [ -V ]
+.RB [ -4 ]
+.RB [ -6 ]
 .SH DESCRIPTION
 .B popa3d
 is a Post Office Protocol version 3 (POP3) server.
@@ -52,6 +54,27 @@ Like
 but staying in the foreground rather than becoming a daemon.
 This supports improved service integration with init systems.
 .TP
+.B -4
+When used with
+.BR -D
+or
+.BR -F ,
+listen on
+.BR 0.0.0.0 .
+.TP
+.B -6
+When used with
+.BR -D
+or
+.BR -F ,
+listen on
+.BR :: .
+If both
+.B -4
+and
+.B -6
+are combined, listen on a dual-stack socket.
+.TP
 .B -V
 Print version information and exit.
 .SH COMMANDS
diff --git a/standalone.c b/standalone.c
index 8fb8a2b..e3a9dd1 100644
--- a/standalone.c
+++ b/standalone.c
@@ -15,6 +15,7 @@
 #include <syslog.h>
 #include <time.h>
 #include <errno.h>
+#include <netdb.h>
 #include <sys/times.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -34,9 +35,20 @@ int deny_severity = SYSLOG_PRI_HI;
 extern int log_error(char *s);
 extern int do_pop_startup(void);
 extern int do_pop_session(void);
+extern int af;
+extern int dual_stack;
 
 typedef volatile sig_atomic_t va_int;
 
+struct ip_addr {
+	sa_family_t af;
+	socklen_t len;
+	union {
+		struct in_addr sin_addr;
+		struct in6_addr sin6_addr;
+	} a;
+};
+
 /*
  * Active POP sessions.  Those that were started within the last MIN_DELAY
  * seconds are also considered active (regardless of their actual state),
@@ -44,7 +56,7 @@ typedef volatile sig_atomic_t va_int;
  * information about sessions that we could have allowed to proceed.
  */
 static struct {
-	struct in_addr addr;		/* Source IP address */
+	struct ip_addr addr;		/* Source IP address */
 	volatile int pid;		/* PID of the server, or 0 for none */
 	clock_t start;			/* When the server was started */
 	clock_t log;			/* When we've last logged a failure */
@@ -102,6 +114,25 @@ static void check_access(int sock)
 }
 #endif
 
+static void save_ip_addr(struct ip_addr *to,
+			 const struct sockaddr *from)
+{
+	to->af = from->sa_family;
+	if (to->af == AF_INET6) {
+		to->a.sin6_addr = ((struct sockaddr_in6 *) from)->sin6_addr;
+		to->len = sizeof to->a.sin6_addr;
+	} else {
+		to->a.sin_addr = ((struct sockaddr_in *) from)->sin_addr;
+		to->len = sizeof to->a.sin_addr;
+	}
+}
+
+static int cmp_ip_addr(const struct ip_addr *a,
+		       const struct ip_addr *b)
+{
+	return memcmp(a, b, ((size_t)&((struct ip_addr *)(0))->a) + a->len);
+}
+
 #if POP_OPTIONS
 int do_standalone(int foreground)
 {
@@ -110,30 +141,59 @@ int main(void)
 {
 	int foreground = 0;
 #endif
-	int true = 1;
+	int off = 0;
+	int on = 1;
 	int sock, new;
-	struct sockaddr_in addr;
+	struct sockaddr_storage addr;
 	socklen_t addrlen;
+	struct ip_addr peer;
 	int pid;
 	struct tms buf;
 	clock_t min_delay, now, log;
 	int i, j, n;
+	struct addrinfo hints, *res;
+	char hbuf[NI_MAXHOST];
+	char sbuf[NI_MAXSERV];
+	int error;
 
 	if (do_pop_startup()) return 1;
 
-	if ((sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
+	snprintf(sbuf, sizeof(sbuf), "%u", DAEMON_PORT);
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_family = af;
+	hints.ai_flags = AI_PASSIVE;
+	error = getaddrinfo(NULL, sbuf, &hints, &res);
+	if (error)
+		return log_error("getaddrinfo");
+
+	sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
+	if (sock < 0) {
+		freeaddrinfo(res);
 		return log_error("socket");
+	}
 
 	if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
-	    (void *)&true, sizeof(true)))
+	    (void *)&on, sizeof(on))) {
+		freeaddrinfo(res);
 		return log_error("setsockopt");
+	}
+
+#ifdef IPV6_V6ONLY
+	if (res->ai_family == AF_INET6 &&
+	    (af == AF_INET6 || dual_stack) &&
+	    setsockopt(sock, IPPROTO_IPV6,
+	    IPV6_V6ONLY, (void *)(dual_stack ? &off : &on), sizeof(on))) {
+		freeaddrinfo(res);
+		return log_error("setsockopt");
+	}
+#endif
 
-	memset(&addr, 0, sizeof(addr));
-	addr.sin_family = AF_INET;
-	addr.sin_addr.s_addr = inet_addr(DAEMON_ADDR);
-	addr.sin_port = htons(DAEMON_PORT);
-	if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)))
+	if (bind(sock, res->ai_addr, res->ai_addrlen)) {
+		freeaddrinfo(res);
 		return log_error("bind");
+	}
+	freeaddrinfo(res);
 
 	if (listen(sock, MAX_BACKLOG))
 		return log_error("listen");
@@ -190,6 +250,17 @@ int main(void)
  */
 		if (new < 0) continue;
 
+		error = getnameinfo((struct sockaddr *)&addr, addrlen,
+				    hbuf, sizeof(hbuf),
+				    NULL, 0, NI_NUMERICHOST);
+		if (error) {
+			log_error("getnameinfo");
+			/* If rendering the numerical address failed,
+			 * no good can come of accepting it! */
+			continue;
+		}
+		save_ip_addr(&peer, (struct sockaddr *) &addr);
+
 		now = times(&buf);
 		if (!now) now = 1;
 
@@ -202,9 +273,9 @@ int main(void)
 			if (sessions[i].pid ||
 			    (sessions[i].start &&
 			    now - sessions[i].start < min_delay)) {
-				if (sessions[i].addr.s_addr ==
-				    addr.sin_addr.s_addr)
-				if (++n >= MAX_SESSIONS_PER_SOURCE) break;
+				if (cmp_ip_addr(&sessions[i].addr, &peer) == 0)
+					if (++n >= MAX_SESSIONS_PER_SOURCE)
+						break;
 			} else
 			if (j < 0) j = i;
 		}
@@ -215,7 +286,7 @@ int main(void)
 			    now - sessions[i].log >= min_delay) {
 				syslog(SYSLOG_PRI_HI,
 					"%s: per source limit reached",
-					inet_ntoa(addr.sin_addr));
+					hbuf);
 				sessions[i].log = now;
 			}
 			continue;
@@ -226,7 +297,7 @@ int main(void)
 			    now < log || now - log >= min_delay) {
 				syslog(SYSLOG_PRI_HI,
 					"%s: sessions limit reached",
-					inet_ntoa(addr.sin_addr));
+					hbuf);
 				log = now;
 			}
 			continue;
@@ -234,8 +305,7 @@ int main(void)
 
 		switch ((pid = fork())) {
 		case -1:
-			syslog(SYSLOG_PRI_ERROR, "%s: fork: %m",
-				inet_ntoa(addr.sin_addr));
+			syslog(SYSLOG_PRI_ERROR, "%s: fork: %m", hbuf);
 			break;
 
 		case 0:
@@ -244,7 +314,7 @@ int main(void)
 			check_access(new);
 #endif
 			syslog(SYSLOG_PRI_LO, "Session from %s",
-				inet_ntoa(addr.sin_addr));
+				hbuf);
 			if (dup2(new, 0) < 0) return log_error("dup2");
 			if (dup2(new, 1) < 0) return log_error("dup2");
 			if (dup2(new, 2) < 0) return log_error("dup2");
@@ -252,7 +322,7 @@ int main(void)
 			return do_pop_session();
 
 		default:
-			sessions[j].addr = addr.sin_addr;
+			sessions[j].addr = peer;
 			sessions[j].pid = pid;
 			sessions[j].start = now;
 			sessions[j].log = 0;
diff --git a/startup.c b/startup.c
index a298015..3dc2630 100644
--- a/startup.c
+++ b/startup.c
@@ -6,6 +6,7 @@
 
 #if POP_OPTIONS
 
+#include <sys/socket.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -28,6 +29,9 @@ extern char *__progname;
 static char *progname;
 #endif
 
+int af = AF_UNSPEC;
+int dual_stack = 0;
+
 static void usage(void)
 {
 	fprintf(stderr, "Usage: %s [-D] [-F] [-V]\n", progname);
@@ -51,7 +55,7 @@ int main(int argc, char **argv)
 		progname = POP_SERVER;
 #endif
 
-	while ((c = getopt(argc, argv, "DFV")) != -1) {
+	while ((c = getopt(argc, argv, "DFV46")) != -1) {
 		switch (c) {
 		case 'F':
 			foreground++;
@@ -59,6 +63,17 @@ int main(int argc, char **argv)
 		case 'D':
 			standalone++;
 			break;
+		case '4':
+			if (af == AF_INET6)
+				dual_stack = 1;
+			else
+				af = AF_INET;
+			break;
+		case '6':
+			if (af == AF_INET)
+				dual_stack = 1;
+			af = AF_INET6;
+			break;
 
 		case 'V':
 			version();
diff --git a/virtual.c b/virtual.c
index bea0bb2..24a9697 100644
--- a/virtual.c
+++ b/virtual.c
@@ -6,7 +6,7 @@
 
 #if POP_VIRTUAL
 
-#define _XOPEN_SOURCE 4
+/* Inhibits NI_MAXHOST definition if present: #define _XOPEN_SOURCE 4 */
 #define _XOPEN_SOURCE_EXTENDED
 #define _XOPEN_VERSION 4
 #define _XPG4_2
@@ -22,6 +22,7 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
+#include <netdb.h>
 #include <arpa/inet.h>
 
 #ifndef NAME_MAX
@@ -42,18 +43,29 @@ int virtual_startup(void)
 
 static char *lookup(void)
 {
-	struct sockaddr_in sin;
+	struct sockaddr_storage ss;
 	socklen_t length;
-
-	length = sizeof(sin);
-	if (getsockname(0, (struct sockaddr *)&sin, &length)) {
-		if (errno == ENOTSOCK) return "";
+	int error;
+	static char hbuf[NI_MAXHOST];
+
+	length = sizeof(ss);
+	if (getsockname(0, (struct sockaddr *)&ss, &length)) {
+		if (errno == ENOTSOCK) {
+			hbuf[0] = '\0';
+			return hbuf;
+		}
 		log_error("getsockname");
 		return NULL;
 	}
-	if (length != sizeof(sin) || sin.sin_family != AF_INET) return NULL;
 
-	return inet_ntoa(sin.sin_addr);
+	error = getnameinfo((struct sockaddr *)&ss, length, hbuf, sizeof(hbuf),
+	    NULL, 0, NI_NUMERICHOST);
+	if (error) {
+		log_error("getnameinfo");
+		return NULL;
+	}
+
+	return hbuf;
 }
 
 static int is_valid_user(char *user)
@@ -118,7 +130,6 @@ struct passwd *virtual_userpass(char *user, char *pass, int *known)
 	}
 	free(pathname);
 
-	if (!(address = strdup(address))) return NULL;
 	virtual_domain = address;
 
 	pathname = concat(VIRTUAL_HOME_PATH, "/", address, "/",