tree-wide: make format_ifname() or friends return negative errno on failure

Also,
- drop unnecessary +1 from buffer size, as IF_NAMESIZE or IFNAMSIZ
  includes the nul at the end.
- format_ifname() does not update buffer on failure,
- introduces format_ifname_alloc(), FORMAT_IFNAME(), and their friends.

13 files changed, 99 insertions, 94 deletions

diff --git a/src/basic/format-util.c b/src/basic/format-util.c
index e2c7b134d0..94501853a1 100644
--- a/src/basic/format-util.c
+++ b/src/basic/format-util.c
@@ -3,23 +3,43 @@
 #include "format-util.h"
 #include "memory-util.h"
 #include "stdio-util.h"
+#include "strxcpyx.h"
+
+assert_cc(STRLEN("%") + DECIMAL_STR_MAX(int) <= IF_NAMESIZE);
+int format_ifname_full(int ifindex, FormatIfnameFlag flag, char buf[static IF_NAMESIZE]) {
+        if (ifindex <= 0)
+                return -EINVAL;
 
-assert_cc(DECIMAL_STR_MAX(int) + 1 <= IF_NAMESIZE + 1);
-char *format_ifname_full(int ifindex, char buf[static IF_NAMESIZE + 1], FormatIfnameFlag flag) {
-        /* Buffer is always cleared */
-        memzero(buf, IF_NAMESIZE + 1);
         if (if_indextoname(ifindex, buf))
-                return buf;
+                return 0;
 
         if (!FLAGS_SET(flag, FORMAT_IFNAME_IFINDEX))
-                return NULL;
+                return -errno;
 
         if (FLAGS_SET(flag, FORMAT_IFNAME_IFINDEX_WITH_PERCENT))
-                assert(snprintf_ok(buf, IF_NAMESIZE + 1, "%%%d", ifindex));
+                assert(snprintf_ok(buf, IF_NAMESIZE, "%%%d", ifindex));
         else
-                assert(snprintf_ok(buf, IF_NAMESIZE + 1, "%d", ifindex));
+                assert(snprintf_ok(buf, IF_NAMESIZE, "%d", ifindex));
 
-        return buf;
+        return 0;
+}
+
+int format_ifname_full_alloc(int ifindex, FormatIfnameFlag flag, char **ret) {
+        char buf[IF_NAMESIZE], *copy;
+        int r;
+
+        assert(ret);
+
+        r = format_ifname_full(ifindex, flag, buf);
+        if (r < 0)
+                return r;
+
+        copy = strdup(buf);
+        if (!copy)
+                return -ENOMEM;
+
+        *ret = copy;
+        return 0;
 }
 
 char *format_bytes_full(char *buf, size_t l, uint64_t t, FormatBytesFlag flag) {
diff --git a/src/basic/format-util.h b/src/basic/format-util.h
index 579f231897..7dd422b987 100644
--- a/src/basic/format-util.h
+++ b/src/basic/format-util.h
@@ -61,11 +61,24 @@ typedef enum {
         FORMAT_IFNAME_IFINDEX_WITH_PERCENT = (1 << 1) | FORMAT_IFNAME_IFINDEX,
 } FormatIfnameFlag;
 
-char *format_ifname_full(int ifindex, char buf[static IF_NAMESIZE + 1], FormatIfnameFlag flag);
-static inline char *format_ifname(int ifindex, char buf[static IF_NAMESIZE + 1]) {
-        return format_ifname_full(ifindex, buf, 0);
+int format_ifname_full(int ifindex, FormatIfnameFlag flag, char buf[static IF_NAMESIZE]);
+int format_ifname_full_alloc(int ifindex, FormatIfnameFlag flag, char **ret);
+
+static inline int format_ifname(int ifindex, char buf[static IF_NAMESIZE]) {
+        return format_ifname_full(ifindex, 0, buf);
+}
+static inline int format_ifname_alloc(int ifindex, char **ret) {
+        return format_ifname_full_alloc(ifindex, 0, ret);
 }
 
+static inline char *_format_ifname_full(int ifindex, FormatIfnameFlag flag, char buf[static IF_NAMESIZE]) {
+        (void) format_ifname_full(ifindex, flag, buf);
+        return buf;
+}
+
+#define FORMAT_IFNAME_FULL(index, flag) _format_ifname_full(index, flag, (char[IF_NAMESIZE]){})
+#define FORMAT_IFNAME(index) _format_ifname_full(index, 0, (char[IF_NAMESIZE]){})
+
 typedef enum {
         FORMAT_BYTES_USE_IEC     = 1 << 0,
         FORMAT_BYTES_BELOW_POINT = 1 << 1,
diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index b5defd10f6..1e66f8700b 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -455,23 +455,23 @@ int sockaddr_pretty(
                         if (r < 0)
                                 return -ENOMEM;
                 } else {
-                        char a[INET6_ADDRSTRLEN], ifname[IF_NAMESIZE + 1];
+                        char a[INET6_ADDRSTRLEN];
 
                         inet_ntop(AF_INET6, &sa->in6.sin6_addr, a, sizeof(a));
-                        if (sa->in6.sin6_scope_id != 0)
-                                format_ifname_full(sa->in6.sin6_scope_id, ifname, FORMAT_IFNAME_IFINDEX);
 
                         if (include_port) {
-                                r = asprintf(&p,
+                                if (asprintf(&p,
                                              "[%s]:%u%s%s",
                                              a,
                                              be16toh(sa->in6.sin6_port),
                                              sa->in6.sin6_scope_id != 0 ? "%" : "",
-                                             sa->in6.sin6_scope_id != 0 ? ifname : "");
-                                if (r < 0)
+                                             FORMAT_IFNAME_FULL(sa->in6.sin6_scope_id, FORMAT_IFNAME_IFINDEX)) < 0)
                                         return -ENOMEM;
                         } else {
-                                p = sa->in6.sin6_scope_id != 0 ? strjoin(a, "%", ifname) : strdup(a);
+                                if (sa->in6.sin6_scope_id != 0)
+                                        p = strjoin(a, "%", FORMAT_IFNAME_FULL(sa->in6.sin6_scope_id, FORMAT_IFNAME_IFINDEX));
+                                else
+                                        p = strdup(a);
                                 if (!p)
                                         return -ENOMEM;
                         }
@@ -1233,7 +1233,7 @@ int socket_bind_to_ifname(int fd, const char *ifname) {
 }
 
 int socket_bind_to_ifindex(int fd, int ifindex) {
-        char ifname[IF_NAMESIZE + 1];
+        char ifname[IF_NAMESIZE];
         int r;
 
         assert(fd >= 0);
@@ -1251,8 +1251,9 @@ int socket_bind_to_ifindex(int fd, int ifindex) {
                 return r;
 
         /* Fall back to SO_BINDTODEVICE on kernels < 5.0 which didn't have SO_BINDTOIFINDEX */
-        if (!format_ifname(ifindex, ifname))
-                return -errno;
+        r = format_ifname(ifindex, ifname);
+        if (r < 0)
+                return r;
 
         return socket_bind_to_ifname(fd, ifname);
 }
diff --git a/src/libsystemd-network/network-common.c b/src/libsystemd-network/network-common.c
index 9bc0da96cd..c8f3305b19 100644
--- a/src/libsystemd-network/network-common.c
+++ b/src/libsystemd-network/network-common.c
@@ -2,11 +2,8 @@
 
 #include "format-util.h"
 #include "network-common.h"
-#include "string-util.h"
 
 const char *get_ifname(int ifindex, char **ifname) {
-        char buf[IF_NAMESIZE + 1];
-
         assert(ifname);
 
         /* This sets ifname only when it is not set yet. */
@@ -14,11 +11,8 @@ const char *get_ifname(int ifindex, char **ifname) {
         if (*ifname)
                 return *ifname;
 
-        if (ifindex <= 0)
-                return NULL;
-
-        if (!format_ifname(ifindex, buf))
+        if (format_ifname_alloc(ifindex, ifname) < 0)
                 return NULL;
 
-        return *ifname = strdup(buf);
+        return *ifname;
 }
diff --git a/src/libsystemd/sd-device/sd-device.c b/src/libsystemd/sd-device/sd-device.c
index b9268dfcd1..7e11ea2d39 100644
--- a/src/libsystemd/sd-device/sd-device.c
+++ b/src/libsystemd/sd-device/sd-device.c
@@ -284,12 +284,12 @@ _public_ int sd_device_new_from_ifname(sd_device **ret, const char *ifname) {
 }
 
 _public_ int sd_device_new_from_ifindex(sd_device **ret, int ifindex) {
-        char ifname[IF_NAMESIZE + 1];
+        char ifname[IF_NAMESIZE];
 
         assert_return(ret, -EINVAL);
         assert_return(ifindex > 0, -EINVAL);
 
-        if (!format_ifname(ifindex, ifname))
+        if (format_ifname(ifindex, ifname) < 0)
                 return -ENODEV;
 
         return device_new_from_main_ifname(ret, ifname);
diff --git a/src/libsystemd/sd-netlink/netlink-util.c b/src/libsystemd/sd-netlink/netlink-util.c
index 886bb48210..49249ca672 100644
--- a/src/libsystemd/sd-netlink/netlink-util.c
+++ b/src/libsystemd/sd-netlink/netlink-util.c
@@ -12,7 +12,7 @@
 int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
         _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *message = NULL;
         _cleanup_strv_free_ char **alternative_names = NULL;
-        char old_name[IF_NAMESIZE + 1] = {};
+        char old_name[IF_NAMESIZE] = {};
         int r;
 
         assert(rtnl);
@@ -33,7 +33,9 @@ int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
                         return log_debug_errno(r, "Failed to remove '%s' from alternative names on network interface %i: %m",
                                                name, ifindex);
 
-                format_ifname(ifindex, old_name);
+                r = format_ifname(ifindex, old_name);
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to get current name of network interface %i: %m", ifindex);
         }
 
         r = sd_rtnl_message_new_link(*rtnl, &message, RTM_SETLINK, ifindex);
diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index c3a2384f15..d18374dda0 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -557,9 +557,9 @@ static void print_machine_status_info(sd_bus *bus, MachineStatusInfo *i) {
                 fputs("\t   Iface:", stdout);
 
                 for (size_t c = 0; c < i->n_netif; c++) {
-                        char name[IF_NAMESIZE+1];
+                        char name[IF_NAMESIZE];
 
-                        if (format_ifname(i->netif[c], name)) {
+                        if (format_ifname(i->netif[c], name) >= 0) {
                                 fputc(' ', stdout);
                                 fputs(name, stdout);
 
diff --git a/src/network/networkctl.c b/src/network/networkctl.c
index d4a7da9f71..32332ac0ba 100644
--- a/src/network/networkctl.c
+++ b/src/network/networkctl.c
@@ -1044,7 +1044,6 @@ static int dump_gateways(
 
         for (int i = 0; i < n; i++) {
                 _cleanup_free_ char *gateway = NULL, *description = NULL;
-                char name[IF_NAMESIZE+1];
 
                 r = in_addr_to_string(local[i].family, &local[i].address, &gateway);
                 if (r < 0)
@@ -1063,7 +1062,7 @@ static int dump_gateways(
                 r = strv_extendf(&buf, "%s%s%s",
                                  gateway,
                                  ifindex <= 0 ? " on " : "",
-                                 ifindex <= 0 ? format_ifname_full(local[i].ifindex, name, FORMAT_IFNAME_IFINDEX_WITH_PERCENT) : "");
+                                 ifindex <= 0 ? FORMAT_IFNAME_FULL(local[i].ifindex, FORMAT_IFNAME_IFINDEX_WITH_PERCENT) : "");
                 if (r < 0)
                         return log_oom();
         }
@@ -1094,7 +1093,6 @@ static int dump_addresses(
 
         for (int i = 0; i < n; i++) {
                 _cleanup_free_ char *pretty = NULL;
-                char name[IF_NAMESIZE+1];
 
                 r = in_addr_to_string(local[i].family, &local[i].address, &pretty);
                 if (r < 0)
@@ -1118,7 +1116,7 @@ static int dump_addresses(
                 r = strv_extendf(&buf, "%s%s%s",
                                  pretty,
                                  ifindex <= 0 ? " on " : "",
-                                 ifindex <= 0 ? format_ifname_full(local[i].ifindex, name, FORMAT_IFNAME_IFINDEX_WITH_PERCENT) : "");
+                                 ifindex <= 0 ? FORMAT_IFNAME_FULL(local[i].ifindex, FORMAT_IFNAME_IFINDEX_WITH_PERCENT) : "");
                 if (r < 0)
                         return log_oom();
         }
@@ -2682,12 +2680,9 @@ static int link_up_down(int argc, char *argv[], void *userdata) {
         SET_FOREACH(p, indexes) {
                 index = PTR_TO_INT(p);
                 r = link_up_down_send_message(rtnl, argv[0], index);
-                if (r < 0) {
-                        char ifname[IF_NAMESIZE + 1];
-
+                if (r < 0)
                         return log_error_errno(r, "Failed to bring %s interface %s: %m",
-                                               argv[0], format_ifname_full(index, ifname, FORMAT_IFNAME_IFINDEX));
-                }
+                                               argv[0], FORMAT_IFNAME_FULL(index, FORMAT_IFNAME_IFINDEX));
         }
 
         return r;
@@ -2720,12 +2715,9 @@ static int link_delete(int argc, char *argv[], void *userdata) {
         SET_FOREACH(p, indexes) {
                 index = PTR_TO_INT(p);
                 r = link_delete_send_message(rtnl, index);
-                if (r < 0) {
-                        char ifname[IF_NAMESIZE + 1];
-
+                if (r < 0)
                         return log_error_errno(r, "Failed to delete interface %s: %m",
-                                               format_ifname_full(index, ifname, FORMAT_IFNAME_IFINDEX));
-                }
+                                               FORMAT_IFNAME_FULL(index, FORMAT_IFNAME_IFINDEX));
         }
 
         return r;
@@ -2844,12 +2836,9 @@ static int verb_reconfigure(int argc, char *argv[], void *userdata) {
         SET_FOREACH(p, indexes) {
                 index = PTR_TO_INT(p);
                 r = bus_call_method(bus, bus_network_mgr, "ReconfigureLink", &error, NULL, "i", index);
-                if (r < 0) {
-                        char ifname[IF_NAMESIZE + 1];
-
+                if (r < 0)
                         return log_error_errno(r, "Failed to reconfigure network interface %s: %m",
-                                               format_ifname_full(index, ifname, FORMAT_IFNAME_IFINDEX));
-                }
+                                               FORMAT_IFNAME_FULL(index, FORMAT_IFNAME_IFINDEX));
         }
 
         return 0;
diff --git a/src/network/networkd-link.c b/src/network/networkd-link.c
index 467f58873c..327815def5 100644
--- a/src/network/networkd-link.c
+++ b/src/network/networkd-link.c
@@ -2212,7 +2212,7 @@ static int link_update_alternative_names(Link *link, sd_netlink_message *message
 }
 
 static int link_update_name(Link *link, sd_netlink_message *message) {
-        char ifname_from_index[IF_NAMESIZE + 1];
+        char ifname_from_index[IF_NAMESIZE];
         const char *ifname;
         int r;
 
@@ -2229,8 +2229,9 @@ static int link_update_name(Link *link, sd_netlink_message *message) {
         if (streq(ifname, link->ifname))
                 return 0;
 
-        if (!format_ifname(link->ifindex, ifname_from_index))
-                return log_link_debug_errno(link, SYNTHETIC_ERRNO(ENXIO), "Could not get interface name for index %i.", link->ifindex);
+        r = format_ifname(link->ifindex, ifname_from_index);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "Could not get interface name for index %i.", link->ifindex);
 
         if (!streq(ifname, ifname_from_index)) {
                 log_link_debug(link, "New interface name '%s' received from the kernel does not correspond "
diff --git a/src/resolve/resolvectl.c b/src/resolve/resolvectl.c
index 076dbe8cd9..c4d9bf5855 100644
--- a/src/resolve/resolvectl.c
+++ b/src/resolve/resolvectl.c
@@ -187,17 +187,19 @@ static void print_source(uint64_t flags, usec_t rtt) {
 }
 
 static void print_ifindex_comment(int printed_so_far, int ifindex) {
-        char ifname[IF_NAMESIZE + 1];
+        char ifname[IF_NAMESIZE];
+        int r;
 
         if (ifindex <= 0)
                 return;
 
-        if (!format_ifname(ifindex, ifname))
-                log_warning_errno(errno, "Failed to resolve interface name for index %i, ignoring: %m", ifindex);
-        else
-                printf("%*s%s-- link: %s%s",
-                       60 > printed_so_far ? 60 - printed_so_far : 0, " ", /* Align comment to the 60th column */
-                       ansi_grey(), ifname, ansi_normal());
+        r = format_ifname(ifindex, ifname);
+        if (r < 0)
+                return (void) log_warning_errno(r, "Failed to resolve interface name for index %i, ignoring: %m", ifindex);
+
+        printf("%*s%s-- link: %s%s",
+               60 > printed_so_far ? 60 - printed_so_far : 0, " ", /* Align comment to the 60th column */
+               ansi_grey(), ifname, ansi_normal());
 }
 
 static int resolve_host(sd_bus *bus, const char *name) {
@@ -1555,15 +1557,16 @@ static int status_ifindex(sd_bus *bus, int ifindex, const char *name, StatusMode
         _cleanup_(link_info_clear) LinkInfo link_info = {};
         _cleanup_(table_unrefp) Table *table = NULL;
         _cleanup_free_ char *p = NULL;
-        char ifi[DECIMAL_STR_MAX(int)], ifname[IF_NAMESIZE + 1] = "";
+        char ifi[DECIMAL_STR_MAX(int)], ifname[IF_NAMESIZE];
         int r;
 
         assert(bus);
         assert(ifindex > 0);
 
         if (!name) {
-                if (!format_ifname(ifindex, ifname))
-                        return log_error_errno(errno, "Failed to resolve interface name for %i: %m", ifindex);
+                r = format_ifname(ifindex, ifname);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to resolve interface name for %i: %m", ifindex);
 
                 name = ifname;
         }
diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index c2fca1fabe..57e0ac3acc 100644
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -504,7 +504,6 @@ static int dns_cache_put_positive(
 
         if (DEBUG_LOGGING) {
                 _cleanup_free_ char *t = NULL;
-                char ifname[IF_NAMESIZE + 1];
 
                 (void) in_addr_to_string(i->owner_family, &i->owner_address, &t);
 
@@ -514,7 +513,7 @@ static int dns_cache_put_positive(
                           i->shared_owner ? " shared" : "",
                           dns_resource_key_to_string(i->key, key_str, sizeof key_str),
                           (i->until - timestamp) / USEC_PER_SEC,
-                          i->ifindex == 0 ? "*" : strna(format_ifname(i->ifindex, ifname)),
+                          i->ifindex == 0 ? "*" : FORMAT_IFNAME(i->ifindex),
                           af_to_name_short(i->owner_family),
                           strna(t));
         }
diff --git a/src/shared/format-table.c b/src/shared/format-table.c
index 806c24ad73..e524aa095e 100644
--- a/src/shared/format-table.c
+++ b/src/shared/format-table.c
@@ -1665,16 +1665,9 @@ static const char *table_data_format(Table *t, TableData *d, bool avoid_uppercas
 
         case TABLE_IFINDEX: {
                 _cleanup_free_ char *p = NULL;
-                char name[IF_NAMESIZE + 1];
 
-                if (format_ifname(d->ifindex, name)) {
-                        p = strdup(name);
-                        if (!p)
-                                return NULL;
-                } else {
-                        if (asprintf(&p, "%i" , d->ifindex) < 0)
-                                return NULL;
-                }
+                if (format_ifname_full_alloc(d->ifindex, FORMAT_IFNAME_IFINDEX, &p) < 0)
+                        return NULL;
 
                 d->formatted = TAKE_PTR(p);
                 break;
diff --git a/src/test/test-nss-hosts.c b/src/test/test-nss-hosts.c
index f9c0bd6ff9..01cbff9b83 100644
--- a/src/test/test-nss-hosts.c
+++ b/src/test/test-nss-hosts.c
@@ -41,14 +41,12 @@ static const char* af_to_string(int family, char *buf, size_t buf_len) {
 }
 
 static int print_gaih_addrtuples(const struct gaih_addrtuple *tuples) {
-        int n = 0;
+        int r, n = 0;
 
         for (const struct gaih_addrtuple *it = tuples; it; it = it->next) {
                 _cleanup_free_ char *a = NULL;
                 union in_addr_union u;
-                int r;
                 char family_name[DECIMAL_STR_MAX(int)];
-                char ifname[IF_NAMESIZE + 1];
 
                 memcpy(&u, it->addr, 16);
                 r = in_addr_to_string(it->family, &u, &a);
@@ -56,21 +54,13 @@ static int print_gaih_addrtuples(const struct gaih_addrtuple *tuples) {
                 if (r == -EAFNOSUPPORT)
                         assert_se(a = hexmem(it->addr, 16));
 
-                if (it->scopeid == 0)
-                        goto numerical_index;
-
-                if (!format_ifname(it->scopeid, ifname)) {
-                        log_warning_errno(errno, "if_indextoname(%d) failed: %m", it->scopeid);
-                numerical_index:
-                        xsprintf(ifname, "%i", it->scopeid);
-                };
-
-                log_info("        \"%s\" %s %s %%%s",
+                log_info("        \"%s\" %s %s %s",
                          it->name,
                          af_to_string(it->family, family_name, sizeof family_name),
                          a,
-                         ifname);
-                n ++;
+                         FORMAT_IFNAME_FULL(it->scopeid, FORMAT_IFNAME_IFINDEX_WITH_PERCENT));
+
+                n++;
         }
         return n;
 }