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 eab788930fa97c320d8484ef18c225aa8a844a6c..bc3e41a56520a56bf1afd04821be2d47e92b06ce 100644 (file)
--- 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 707b7a22a36a4f2e20f4fa5f33f09e0a8fdb4a25..0260ae7ab1d155cd051c2f52297ba92b13b49ac2 100644 (file)
--- 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;
 };