[GRO] check whether ip_id continuity needs to be checked when two TCP packets are merged.

[jiangheng (G)]

Hi jiayu.hu

It cannot be guaranteed that 16bit identification field of ip packets in the 
same tcp stream will be continuous.
Please help check whether ip_id continuity needs to be checked when two TCP 
packets are merged?
Seems to modify the following code, gro will aggregate better, and work better:

diff --git a/lib/gro/gro_tcp4.h b/lib/gro/gro_tcp4.h
index 212f97a042..06faead7b5 100644
--- a/lib/gro/gro_tcp4.h
+++ b/lib/gro/gro_tcp4.h
@@ -291,12 +291,10 @@ check_seq_option(struct gro_tcp4_item *item,
        /* check if the two packets are neighbors */
        len = pkt_orig->pkt_len - l2_offset - pkt_orig->l2_len -
                pkt_orig->l3_len - tcp_hl_orig;
-       if ((sent_seq == item->sent_seq + len) && (is_atomic ||
-                               (ip_id == item->ip_id + 1)))
+       if (sent_seq == item->sent_seq + len)
                /* append the new packet */
                return 1;
-       else if ((sent_seq + tcp_dl == item->sent_seq) && (is_atomic ||
-                               (ip_id + item->nb_merged == item->ip_id)))
+       else if (sent_seq + tcp_dl == item->sent_seq)
                /* pre-pend the new packet */
                return -1;