From: Vincent Bernat <vincent@bernat.im>
Date: Sat, 14 May 2016 17:46:07 +0000 (+0200)
Subject: interfaces: ensure we don't break strict aliasing rule
X-Git-Tag: 0.9.3~22
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b562f01fe4fdd24e6819f383e65017b680a159f5;p=thirdparty%2Flldpd.git

interfaces: ensure we don't break strict aliasing rule

Use an union to manipulate IPv4/IPv6 address. Other occurrences are
using memcpy (notably with "struct sockaddr_storage"). This is
preventive since gcc seems to rely more on this strict aliasing rule
since gcc-6.
---

diff --git a/src/daemon/interfaces.c b/src/daemon/interfaces.c
index eab78893..bc3e41a5 100644
--- a/src/daemon/interfaces.c
+++ b/src/daemon/interfaces.c
@@ -376,8 +376,8 @@ interfaces_helper_mgmt_for_af(struct lldpd *cfg,
 	struct lldpd_mgmt *mgmt;
 	char addrstrbuf[INET6_ADDRSTRLEN];
 	int found = 0;
-	void *sin_addr_ptr;
-	size_t sin_addr_size;
+	union lldpd_address in_addr;
+	size_t in_addr_size;
 
 	TAILQ_FOREACH(addr, addrs, next) {
 		if (addr->address.ss_family != lldpd_af(af))
@@ -385,24 +385,26 @@ interfaces_helper_mgmt_for_af(struct lldpd *cfg,
 
 		switch (af) {
 		case LLDPD_AF_IPV4:
-			sin_addr_ptr = &((struct sockaddr_in *)&addr->address)->sin_addr;
-			sin_addr_size = sizeof(struct in_addr);
+			in_addr_size = sizeof(struct in_addr);
+			memcpy(&in_addr, &((struct sockaddr_in *)&addr->address)->sin_addr,
+			    in_addr_size);
 			if (global) {
-				if (!IN_IS_ADDR_GLOBAL((struct in_addr *)sin_addr_ptr))
+				if (!IN_IS_ADDR_GLOBAL(&in_addr.inet))
 					continue;
 			} else {
-				if (!IN_IS_ADDR_LINKLOCAL((struct in_addr *)sin_addr_ptr))
+				if (!IN_IS_ADDR_LINKLOCAL(&in_addr.inet))
 					continue;
 			}
 			break;
 		case LLDPD_AF_IPV6:
-			sin_addr_ptr = &((struct sockaddr_in6 *)&addr->address)->sin6_addr;
-			sin_addr_size = sizeof(struct in6_addr);
+			in_addr_size = sizeof(struct in6_addr);
+			memcpy(&in_addr, &((struct sockaddr_in6 *)&addr->address)->sin6_addr,
+			    in_addr_size);
 			if (global) {
-				if (!IN6_IS_ADDR_GLOBAL((struct in6_addr *)sin_addr_ptr))
+				if (!IN6_IS_ADDR_GLOBAL(&in_addr.inet6))
 					continue;
 			} else {
-				if (!IN6_IS_ADDR_LINKLOCAL((struct in6_addr *)sin_addr_ptr))
+				if (!IN6_IS_ADDR_LINKLOCAL(&in_addr.inet6))
 					continue;
 			}
 			break;
@@ -410,14 +412,14 @@ interfaces_helper_mgmt_for_af(struct lldpd *cfg,
 			assert(0);
 			continue;
 		}
-		if (inet_ntop(lldpd_af(af), sin_addr_ptr,
+		if (inet_ntop(lldpd_af(af), &in_addr,
 			addrstrbuf, sizeof(addrstrbuf)) == NULL) {
 			log_warn("interfaces", "unable to convert IP address to a string");
 			continue;
 		}
 		if (cfg->g_config.c_mgmt_pattern == NULL ||
 		    pattern_match(addrstrbuf, cfg->g_config.c_mgmt_pattern, allnegative)) {
-			mgmt = lldpd_alloc_mgmt(af, sin_addr_ptr, sin_addr_size,
+			mgmt = lldpd_alloc_mgmt(af, &in_addr, in_addr_size,
 			    addr->index);
 			if (mgmt == NULL) {
 				assert(errno == ENOMEM); /* anything else is a bug */
diff --git a/src/lldpd-structs.h b/src/lldpd-structs.h
index 707b7a22..0260ae7a 100644
--- a/src/lldpd-structs.h
+++ b/src/lldpd-structs.h
@@ -148,14 +148,15 @@ lldpd_af(int af)
 }
 
 #define LLDPD_MGMT_MAXADDRSIZE	16 /* sizeof(struct in6_addr) */
+union lldpd_address {
+	struct in_addr		inet;
+	struct in6_addr		inet6;
+	u_int8_t		octets[LLDPD_MGMT_MAXADDRSIZE]; /* network byte order! */
+};
 struct lldpd_mgmt {
 	TAILQ_ENTRY(lldpd_mgmt) m_entries;
-	int				m_family;
-	union {
-		struct in_addr		inet;
-		struct in6_addr		inet6;
-		u_int8_t		octets[LLDPD_MGMT_MAXADDRSIZE]; /* network byte order! */
-	} m_addr;
+	int			m_family;
+	union lldpd_address	m_addr;
 	size_t 			m_addrsize;
 	u_int32_t		m_iface;
 };