[netsniff-ng] [PATCH 5/7] trafgen: l2: Add VLAN header generation

[Vadim Kochan]

Add generation of VLAN header with supported fields:

    TPID, DEI/CFI, PCP, VID

Changed struct proto_field.offset uint16_t -> int16_t to make
TPID offset -2 to point to ether type.

Signed-off-by: Vadim Kochan <vadi...@gmail.com>
---
 trafgen_l2.c    | 63 ++++++++++++++++++++++++++++++++++++++++++++++++---------
 trafgen_l2.h    |  9 +++++++++
 trafgen_proto.h |  4 +++-
 3 files changed, 65 insertions(+), 11 deletions(-)

diff --git a/trafgen_l2.c b/trafgen_l2.c
index c0e92a3..a7387b8 100644
--- a/trafgen_l2.c
+++ b/trafgen_l2.c
@@ -17,25 +17,25 @@ static struct proto_field eth_fields[] = {
        { .id = ETH_TYPE,     .len = 2, .offset = 12 },
 };
 
-static void eth_set_next_proto(struct proto_hdr *hdr, enum proto_id pid)
+static uint16_t pid_to_eth(enum proto_id pid)
 {
-       uint16_t eth_type;
-
        switch(pid) {
        case PROTO_ARP:
-               eth_type = ETH_P_ARP;
-               break;
+               return ETH_P_ARP;
        case PROTO_IP4:
-               eth_type = ETH_P_IP;
-               break;
+               return ETH_P_IP;
        case PROTO_IP6:
-               eth_type = ETH_P_IPV6;
-               break;
+               return ETH_P_IPV6;
+       case PROTO_VLAN:
+               return ETH_P_8021Q;
        default:
                panic("eth: Not supported protocol id %u\n", pid);
        }
+}
 
-       proto_field_set_default_be16(hdr, ETH_TYPE, eth_type);
+static void eth_set_next_proto(struct proto_hdr *hdr, enum proto_id pid)
+{
+       proto_field_set_default_be16(hdr, ETH_TYPE, pid_to_eth(pid));
 }
 
 static void eth_header_init(struct proto_hdr *hdr)
@@ -52,6 +52,48 @@ static struct proto_hdr eth_hdr = {
        .set_next_proto = eth_set_next_proto,
 };
 
+static struct proto_field vlan_fields[] = {
+       /* TPID overlaps with Ethernet header and points to ether type */
+       { .id = VLAN_TPID, .len = 2, .offset = -2 },
+       { .id = VLAN_TCI,  .len = 2, .offset = 0 },
+       { .id = VLAN_PCP,  .len = 2, .offset = 0, .shift = 13, .mask = 0xe000 },
+       { .id = VLAN_DEI,  .len = 2, .offset = 0, .shift = 12, .mask = 0x1000 },
+       { .id = VLAN_VID,  .len = 2, .offset = 0, .shift = 0,  .mask = 0xfff },
+       /* Original ether type is stored after VLAN header */
+       { .id = VLAN_ETYPE, .len = 2, .offset = 2 },
+};
+
+static void vlan_header_init(struct proto_hdr *hdr)
+{
+       struct proto_hdr *lower;
+       uint16_t lower_etype = 0;
+
+       lower = proto_lower_default_add(hdr, PROTO_ETH);
+
+       proto_header_fields_add(hdr, vlan_fields, array_size(vlan_fields));
+
+       if (lower->id == PROTO_ETH)
+               lower_etype = proto_field_get_u16(lower, ETH_TYPE);
+       else if (lower->id == PROTO_VLAN)
+               lower_etype = proto_field_get_u16(lower, VLAN_ETYPE);
+
+       proto_field_set_be16(hdr, VLAN_ETYPE, lower_etype);
+       proto_field_set_default_be16(hdr, VLAN_TPID, pid_to_eth(hdr->id));
+}
+
+static void vlan_set_next_proto(struct proto_hdr *hdr, enum proto_id pid)
+{
+       if (pid != PROTO_VLAN)
+               proto_field_set_be16(hdr, VLAN_ETYPE, pid_to_eth(pid));
+}
+
+static struct proto_hdr vlan_hdr = {
+       .id             = PROTO_VLAN,
+       .layer          = PROTO_L2,
+       .header_init    = vlan_header_init,
+       .set_next_proto = vlan_set_next_proto,
+};
+
 static struct proto_field arp_fields[] = {
        { .id = ARP_HTYPE, .len = 2 },
        { .id = ARP_PTYPE, .len = 2, .offset = 2 },
@@ -98,5 +140,6 @@ static struct proto_hdr arp_hdr = {
 void protos_l2_init(void)
 {
        proto_header_register(&eth_hdr);
+       proto_header_register(&vlan_hdr);
        proto_header_register(&arp_hdr);
 }
diff --git a/trafgen_l2.h b/trafgen_l2.h
index 38727ec..9beb2aa 100644
--- a/trafgen_l2.h
+++ b/trafgen_l2.h
@@ -19,6 +19,15 @@ enum arp_field {
        ARP_TPA,
 };
 
+enum vlan_field {
+       VLAN_TPID,
+       VLAN_TCI,
+       VLAN_PCP,
+       VLAN_DEI,
+       VLAN_VID,
+       VLAN_ETYPE,
+};
+
 extern void protos_l2_init(void);
 
 #endif /* TRAFGEN_L2_H */
diff --git a/trafgen_proto.h b/trafgen_proto.h
index 491e079..996c24e 100644
--- a/trafgen_proto.h
+++ b/trafgen_proto.h
@@ -12,6 +12,7 @@ struct proto_ctx {
 enum proto_id {
        PROTO_NONE,
        PROTO_ETH,
+       PROTO_VLAN,
        PROTO_ARP,
        PROTO_IP4,
        PROTO_IP6,
@@ -31,7 +32,8 @@ struct proto_field {
        size_t len;
        uint32_t shift;
        uint32_t mask;
-       uint16_t offset;
+       /* might be negative (e.g. VLAN TPID field) */
+       int16_t offset;
 
        bool is_set;
        uint16_t pkt_offset;
-- 
2.6.3

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