[netsniff-ng] [PATCH v3 10/15] trafgen: tcp: Update csum at runtime if it needed

[Vadim Kochan]

Update TCP checksum field if any TCP of fields was changed.
Use same checksum update function on 'packet_finish' and 'header update'.

Set 'is_csum_valid = false' if lower IPv4/IPv6 pseudo header was changed.

Signed-off-by: Vadim Kochan <vadi...@gmail.com>
---
 trafgen_l3.c |  4 ++--
 trafgen_l4.c | 18 +++++++++++++++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/trafgen_l3.c b/trafgen_l3.c
index 91052a0..e6aa516 100644
--- a/trafgen_l3.c
+++ b/trafgen_l3.c
@@ -50,7 +50,7 @@ static void ipv4_field_changed(struct proto_field *field)
        if (field->id == IP4_SADDR || field->id == IP4_DADDR) {
                struct proto_hdr *upper = proto_upper_header(field->hdr);
 
-               if (upper && upper->ops->id == PROTO_UDP)
+               if (upper && (upper->ops->id == PROTO_UDP || upper->ops->id == 
PROTO_TCP))
                        upper->is_csum_valid = false;
        }
 }
@@ -148,7 +148,7 @@ static void ipv6_field_changed(struct proto_field *field)
        if (field->id == IP6_SADDR || field->id == IP6_DADDR) {
                struct proto_hdr *upper = proto_upper_header(field->hdr);
 
-               if (upper && upper->ops->id == PROTO_UDP)
+               if (upper && (upper->ops->id == PROTO_UDP || upper->ops->id == 
PROTO_TCP))
                        upper->is_csum_valid = false;
        }
 }
diff --git a/trafgen_l4.c b/trafgen_l4.c
index ee8deb4..b3b0775 100644
--- a/trafgen_l4.c
+++ b/trafgen_l4.c
@@ -118,13 +118,20 @@ static void tcp_header_init(struct proto_hdr *hdr)
        proto_field_set_default_be16(hdr, TCP_DOFF, 5);
 }
 
-static void tcp_packet_finish(struct proto_hdr *hdr)
+static void tcp_field_changed(struct proto_field *field)
+{
+       field->hdr->is_csum_valid = false;
+}
+
+static void tcp_csum_update(struct proto_hdr *hdr)
 {
        struct proto_hdr *lower = proto_lower_header(hdr);
        struct packet *pkt = current_packet();
        uint16_t total_len;
        uint16_t csum;
 
+       if (hdr->is_csum_valid)
+               return;
        if (proto_field_is_set(hdr, TCP_CSUM))
                return;
 
@@ -133,6 +140,8 @@ static void tcp_packet_finish(struct proto_hdr *hdr)
 
        total_len = pkt->len - hdr->pkt_offset;
 
+       proto_field_set_default_be16(hdr, TCP_CSUM, 0);
+
        switch (lower->ops->id) {
        case PROTO_IP4:
                csum = p4_csum((void *) proto_header_ptr(lower), 
proto_header_ptr(hdr),
@@ -147,14 +156,17 @@ static void tcp_packet_finish(struct proto_hdr *hdr)
                break;
        }
 
-       proto_field_set_be16(hdr, TCP_CSUM, bswap_16(csum));
+       proto_field_set_default_be16(hdr, TCP_CSUM, bswap_16(csum));
+       hdr->is_csum_valid = true;
 }
 
 static const struct proto_ops tcp_proto_ops = {
        .id             = PROTO_TCP,
        .layer          = PROTO_L4,
        .header_init    = tcp_header_init,
-       .packet_finish  = tcp_packet_finish,
+       .packet_update  = tcp_csum_update,
+       .packet_finish  = tcp_csum_update,
+       .field_changed  = tcp_field_changed,
 };
 
 static struct proto_field icmpv4_fields[] = {
-- 
2.9.2

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