sd-dhcp-client/net-util: make netmask_to_prefixlen generic

This was originally included in the dhcp-client at my request, but it is not
really dhcp-specific and useful outside of it, so let's pull it out.

2 files changed, 18 insertions, 0 deletions

diff --git a/src/shared/net-util.c b/src/shared/net-util.c
index 887dae5125..630be18e56 100644
--- a/src/shared/net-util.c
+++ b/src/shared/net-util.c
@@ -58,6 +58,21 @@ bool net_match_config(const struct ether_addr *match_mac,
         return 1;
 }
 
+unsigned net_netmask_to_prefixlen(const struct in_addr *addr) {
+        unsigned len = 0;
+        uint32_t mask;
+
+        assert(addr);
+
+        mask = be32toh(addr->s_addr);
+        while (mask) {
+                len++;
+                mask = mask << 1;
+        }
+
+        return len;
+}
+
 int config_parse_ifname(const char *unit,
                         const char *filename,
                         unsigned line,
diff --git a/src/shared/net-util.h b/src/shared/net-util.h
index c7edfb96f0..0ec04db87e 100644
--- a/src/shared/net-util.h
+++ b/src/shared/net-util.h
@@ -22,6 +22,7 @@
 #pragma once
 
 #include <netinet/ether.h>
+#include <netinet/in.h>
 #include <stdbool.h>
 
 bool net_match_config(const struct ether_addr *match_mac,
@@ -35,6 +36,8 @@ bool net_match_config(const struct ether_addr *match_mac,
                       const char *dev_type,
                       const char *dev_name);
 
+unsigned net_netmask_to_prefixlen(const struct in_addr *netmask);
+
 int config_parse_hwaddr(const char *unit, const char *filename, unsigned line,
                         const char *section, unsigned section_line, const char *lvalue,
                         int ltype, const char *rvalue, void *data, void *userdata);