First working prototype - DHCPv4

dhcp-relay/Makefile

@@ -4,6 +4,7 @@ USER_TARGETS := dhcp_user_xdp
 BPF_TARGETS :=dhcp_kern_xdp 
 EXTRA_DEPS := dhcp-relay.h
 #EXTRA_CFLAGS := $(if $(IPV6),-DIPV6)
+EXTRA_CFLAGS := -fno-builtin
 
 LIB_DIR = ../lib
 

dhcp-relay/dhcp-relay.h

@@ -10,19 +10,21 @@
 #define DHO_DHCP_AGENT_OPTIONS 82
 #define RAI_CIRCUIT_ID 1
 #define RAI_REMOTE_ID 2
-#define RAI_OPTION_LEN 40
+#define RAI_OPTION_LEN IF_NAMESIZE
 #define VLAN_ASCII_MAX 4 /* Max bytes needed to store VLAN in ASCII format */
 
 #define DHCP_SERVER_PORT 67
 #define DHCP_CLIENT_PORT 68
 #define DHCP_REQUEST 1
 #define DHCP_REPLY 2
 
+#define MAX_LOOPS 40
+
 /* Structure for sub-options in option 82 */
 struct sub_option {
  __u8 option_id;
  __u8 len;
- char val[IF_NAMESIZE];
+ char val[RAI_OPTION_LEN];
 };
 
 /*structure for dhcp option 82 */

dhcp-relay/dhcp_kern_xdp.c

@@ -8,6 +8,13 @@
 #include <xdp/context_helpers.h>
 #include "dhcp-relay.h"
 
+#define bpf_printk(fmt, ...) \
+({ \
+ char ____fmt[] = fmt; \
+ bpf_trace_printk(____fmt, sizeof(____fmt), \
+ ##__VA_ARGS__); \
+})
+
 /*
  * This map is for storing the DHCP relay configuration, including:
  * 
@@ -49,76 +56,104 @@ struct {
  __uint(max_entries, 16384);
 } client_vlans SEC(".maps");
 
+void memcpy_var(void *to, void *from, __u64 len) {
+ __u8 *t8 = to, *f8 = from;
+ int i;
+
+ for (i = 0; i < len && i < MAX_LOOPS; i++) {
+ *t8++ = *f8++; 
+ }
+
+}
+
+void memset_var(void *d, __u8 c, __u64 len) {
+ __u8 *d8 = d;
+ int i;
+
+ for (i = 0; i < len && i < MAX_LOOPS; i++) {
+ *d8++ = c;
+ }
+
+}
+
 /* Inserts DHCP option 82 into the received DHCP packet
  * at the specified offset.
  */
 static __always_inline int write_dhcp_option_82(void *ctx, int offset,
  struct collect_vlans *vlans, char *dev) {
+
  struct dhcp_option_82 option;
-
+
+ static __u8 buf[RAI_OPTION_LEN];
+
  option.t = DHO_DHCP_AGENT_OPTIONS;
  option.len = sizeof (struct sub_option) + sizeof (struct sub_option);
  option.circuit_id.option_id = RAI_CIRCUIT_ID;
- option.circuit_id.len = sizeof(option.circuit_id.val);
+ option.circuit_id.len = sizeof (option.circuit_id.val);
+ option.remote_id.option_id = RAI_REMOTE_ID;
+ option.remote_id.len = sizeof (option.remote_id.val);
+
+ /* Initialize val arrays */
+ memset_var(option.circuit_id.val, 0, sizeof (option.circuit_id.val));
+ memset_var(option.remote_id.val, '*', sizeof (option.remote_id.val));
+ //memset(option.circuit_id.val, 0, sizeof (option.circuit_id.val));
+ //memset(option.remote_id.val, '*', sizeof (option.remote_id.val));
 
  /* Reconstruct VLAN device name
  * Convert VLAN tags to ASCII from right to left, starting with
  * inner VLAN tag.
- * Device name is 16 characters long and prepended with dash, e.g.:
- * ----ens6f0.83.20
- * We avoid null bytes to ensure compatibility with DHCP servers that
- * interpret null as a string terminator.
+ * Device name is up to 16 characters long - remaining buffer space
+ * contains null bytes.
  */
-
- char buf[IF_NAMESIZE];
- memset(buf, '-', sizeof (buf));
+
+ memset(buf, 0, sizeof (buf));
+
+ int c = VLAN_ASCII_MAX; /* We will need 4 bytes at most */
+ int i = RAI_OPTION_LEN - 1;
 
- int c = VLAN_ASCII_MAX; /* We will need 4 bytes at most */
- int i = IF_NAMESIZE - 1;
  __u16 inner_vlan = vlans->id[1];
  __u16 outer_vlan = vlans->id[0];
-
+
+ /* Convert inner VLAN to ASCII */
+#pragma unroll VLAN_ASCII_MAX
  for (c = VLAN_ASCII_MAX; c > 0; c--) {
  buf[i--] = (inner_vlan % 10) + '0';
  inner_vlan /= 10;
  if (inner_vlan == 0) {
  break;
  }
  }
- 
+
  buf[i--] = '.';
-
+
+ /* Convert outer VLAN to ASCII */
+#pragma unroll VLAN_ASCII_MAX 
  for (c = VLAN_ASCII_MAX; c > 0; c--) {
  buf[i--] = (outer_vlan % 10) + '0';
  outer_vlan /= 10;
  if (outer_vlan == 0) {
  break;
  }
  }
-
 
  buf[i--] = '.';
-
- for (c = IF_NAMESIZE - 1; c >= 0; c--) {
 
- if (dev[c] != 0) {
+ /* Append interface name */
+#pragma unroll RAI_OPTION_LEN
+ for (c = RAI_OPTION_LEN - 1; c >= 0; c--) {
+ if (dev[c] != 0)
  buf[i--] = dev[c];
- }
-
- if (i < 0) {
- break;
- }
-
- }
-
- if(sizeof(option.circuit_id.val) == sizeof(buf)) {
- memcpy(option.circuit_id.val, buf, sizeof(buf));
+ if (i < 0)
+ break; 
  }
 
- /* Initialize remote ID */
- memset(option.remote_id.val, 0, sizeof(option.remote_id.val));
- option.remote_id.option_id = RAI_REMOTE_ID;
- option.remote_id.len = sizeof(option.remote_id.val);
+ i++;
+
+ /* Copy resulting interface name to circuit_id */
+ if (sizeof (option.circuit_id.val) == sizeof (buf)) {
+ memcpy_var(option.circuit_id.val, buf + i, sizeof (buf) - i);
+ //memcpy_var(option.circuit_id.val, buf, sizeof (buf));
+ }
 
  return xdp_store_bytes(ctx, offset, &option, sizeof (option), 0);
 }
@@ -166,13 +201,6 @@ static __always_inline int calc_ip_csum(struct iphdr *oldip, struct iphdr *ip,
  */
 //static __u8 buf[static_offset + VLAN_MAX_DEPTH * sizeof (struct vlan_hdr)];
 
-#define bpf_printk(fmt, ...) \
-({ \
- char ____fmt[] = fmt; \
- bpf_trace_printk(____fmt, sizeof(____fmt), \
- ##__VA_ARGS__); \
-})
-
 /* XDP program for parsing the DHCP packet and inserting the option 82*/
 SEC(XDP_PROG_SEC)
 int xdp_dhcp_relay(struct xdp_md *ctx) {
@@ -183,10 +211,10 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
  int res = bpf_xdp_adjust_tail(ctx, delta);
  if (res != 0) {
  bpf_printk("Cannot tail extend packet, delta %i - error code %i", delta, res);
- return XDP_ABORTED;
+ return XDP_PASS;
  }
 
- bpf_printk("Tail extended packet by %i bytes", delta);
+ //bpf_printk("Tail extended packet by %i bytes", delta);
 
  void *data_end = (void *) (long) ctx->data_end;
  void *data = (void *) (long) ctx->data;
@@ -217,27 +245,34 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
  int key = 0;
  int len = 0;
 
- if (data + 1 > data_end)
- return XDP_ABORTED;
+ if (data + 1 > data_end) {
+ bpf_printk("Empty packet\n");
+ goto out;
+ }
 
  nh.pos = data;
  ether_type = parse_ethhdr_vlan(&nh, data_end, &eth, &vlans);
  /* check for valid ether type */
  if (ether_type < 0) {
- bpf_printk("Cannot determine ethertype");
- rc = XDP_ABORTED;
+ bpf_printk("Cannot determine ethertype\n");
  goto out;
  }
+
  if (ether_type != bpf_htons(ETH_P_IP)) {
- bpf_printk("Ethertype %#x is not ETH_P_IP", bpf_ntohs(ether_type));
+ //bpf_printk("Ethertype %x is not ETH_P_IP\n", bpf_ntohs(ether_type));
  goto out;
  }
 
- bpf_printk("Ethertype %x", bpf_ntohs(ether_type));
-
+ bpf_printk("Ethertype %x\n", bpf_ntohs(ether_type));
+ 
  /* Check at least two vlan tags are present */
+ if (vlans.id[0] == 0) {
+ bpf_printk("No outer VLAN tag set\n");
+ goto out;
+ }
+
  if (vlans.id[1] == 0) {
- bpf_printk("No VLAN tags set");
+ bpf_printk("No inner VLAN tag set\n");
  goto out;
  }
 
@@ -264,6 +299,8 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
 
  /* Increase UDP length header */
  udp->len += bpf_htons(delta);
+
+ udp->check = 0;
 
  /* Read DHCP server IP from config map */
  key = 0;
@@ -294,6 +331,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
  // goto out;
 
  /* Increment offset by 4 bytes for each VLAN (to accomodate VLAN headers */
+#pragma unroll VLAN_MAX_DEPTH
  for (i = 0; i < VLAN_MAX_DEPTH; i++) {
  if (vlans.id[i]) {
 
@@ -426,7 +464,7 @@ int xdp_dhcp_relay(struct xdp_md *ctx) {
  bpf_printk("Could not write DHCP option 82 at offset %i", option_offset);
  return XDP_ABORTED;
  }
-
+ 
  /* Set END option */
 
  /* Verifier check */