dhcp-network: enable IP_FREEBIND for UDP sockets

[elogind.git] / src / libsystemd-network / dhcp-network.c

diff --git a/src/libsystemd-network/dhcp-network.c b/src/libsystemd-network/dhcp-network.c
index dd26ef3e002df3ad5531eb084bb00ffdb59fb76a..29276c0559b07a90213a95da9cb5395ff26d5b41 100644 (file)
--- a/src/libsystemd-network/dhcp-network.c
+++ b/src/libsystemd-network/dhcp-network.c
@@ -33,15 +33,22 @@
 #include "dhcp-internal.h"
 
 int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
-                                 uint32_t xid) {
+                                 uint32_t xid, struct ether_addr mac_addr) {
         struct sock_filter filter[] = {
             BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
             BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
-            /* TODO: match ip.version */
             BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+            BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
+            BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
+            BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
+            BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+            BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
+            BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
+            BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
+            BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
             BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_PORT_CLIENT, 1, 0),           /* UDP destination port == DHCP client port ? */
             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
@@ -57,7 +64,18 @@ int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
             BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
-            /* TODO: match chaddr */
+            BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((unsigned int *) &mac_addr))),                    /* A <- 4 bytes of client's MAC */
+            BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
+            BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),                 /* A <- 4 bytes of MAC from dhcp.chaddr */
+            BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
+            BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
+            BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
+            BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((unsigned short *) (((char *) &mac_addr) + 4)))), /* A <- remainder of client's MAC */
+            BPF_STMT(BPF_MISC + BPF_TAX, 0),                                                       /* X <- A */
+            BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),             /* A <- remainder of MAC from dhcp.chaddr */
+            BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                                /* A xor X */
+            BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                                          /* A == 0 ? */
+            BPF_STMT(BPF_RET + BPF_K, 0),                                                          /* ignore */
             BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
             BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
             BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
@@ -68,7 +86,7 @@ int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
             .filter = filter
         };
         _cleanup_close_ int s = -1;
-        int r, one = 1;
+        int r, on = 1;
 
         assert(index > 0);
         assert(link);
@@ -77,7 +95,7 @@ int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
         if (s < 0)
                 return -errno;
 
-        r = setsockopt (s, SOL_PACKET, PACKET_AUXDATA, &one, sizeof(one));
+        r = setsockopt (s, SOL_PACKET, PACKET_AUXDATA, &on, sizeof(on));
         if (r < 0)
                 return -errno;
 
@@ -108,7 +126,7 @@ int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
                 .in.sin_addr.s_addr = address,
         };
         _cleanup_close_ int s = -1;
-        int r, tos = IPTOS_CLASS_CS6;
+        int r, on = 1, tos = IPTOS_CLASS_CS6;
 
         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
         if (s < 0)
@@ -118,6 +136,24 @@ int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
         if (r < 0)
                 return -errno;
 
+        r = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
+        if (r < 0)
+                return -errno;
+
+        if (address == INADDR_ANY) {
+                r = setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
+                if (r < 0)
+                        return -errno;
+
+                r = setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
+                if (r < 0)
+                        return -errno;
+        } else {
+                r = setsockopt(s, IPPROTO_IP, IP_FREEBIND, &on, sizeof(on));
+                if (r < 0)
+                        return -errno;
+        }
+
         r = bind(s, &src.sa, sizeof(src.in));
         if (r < 0)
                 return -errno;