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Unverified Commit 4b37c92c by Sam Boyles Committed by Christian Brauner
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Improve efficiency of lxc_ifname_alnum_case_sensitive

To detect if a newly generated interface name is a duplicate of an existing interface lxc_ifname_alnum_case_sensitive() currently gets a list of all interfaces using netns_getifaddrs(). When the system has a small number of interfaces this works fine, however when there are thousands or tens of thousands of interfaces this quickly becomes less than optimal. As we only need to check if an interface name exists, and do not need the detailed information about the interfaces provided by netns_getifaddrs(), we can instead use the if_nametoindex() function, which is much more efficient. Signed-off-by: 's avatarSam Boyles <sam.boyles@alliedtelesis.co.nz>
parent f518238a
Showing with 2 additions and 18 deletions
src/lxc/network.c
......@@ -2438,9 +2438,7 @@ static const char padchar[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLM
char *lxc_ifname_alnum_case_sensitive(char *template)
{
int ret;
struct netns_ifaddrs *ifa, *ifaddr;
char name[IFNAMSIZ];
bool exists = false;
size_t i = 0;
#ifdef HAVE_RAND_R
unsigned int seed;
......@@ -2454,18 +2452,11 @@ char *lxc_ifname_alnum_case_sensitive(char *template)
if (strlen(template) >= IFNAMSIZ)
return NULL;
/* Get all the network interfaces. */
ret = netns_getifaddrs(&ifaddr, -1, &(bool){false});
if (ret < 0)
return log_error_errno(NULL, errno, "Failed to get network interfaces");
/* Generate random names until we find one that doesn't exist. */
for (;;) {
name[0] = '\0';
(void)strlcpy(name, template, IFNAMSIZ);
exists = false;
for (i = 0; i < strlen(name); i++) {
if (name[i] == 'X') {
#ifdef HAVE_RAND_R
......@@ -2476,18 +2467,11 @@ char *lxc_ifname_alnum_case_sensitive(char *template)
}
}
for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
if (!strcmp(ifa->ifa_name, name)) {
exists = true;
break;
}
}
if (!exists)
if (if_nametoindex(name) == 0) {
break;
}
}
netns_freeifaddrs(ifaddr);
(void)strlcpy(template, name, strlen(template) + 1);
return template;
......
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