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osmo-gtp-kernel
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gtp: use lookup table to calculate gtp1u header length 

Based on Harald's suggestion from the code.
This commit is contained in:
Pablo Neira Ayuso 2014-02-18 16:26:39 +01:00
parent 28da979257
commit c993e26f15
2 changed files with 14 additions and 14 deletions
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27
gtp.c
View File

@ -261,6 +261,17 @@ out:
return -1;
}
static u8 gtp1u_header_len[] = {
[0] = 0, /* 0 */
[GTP1_F_SEQ] = 2, /* 2 */
[GTP1_F_NPDU] = 1, /* 1 */
[GTP1_F_SEQ|GTP1_F_NPDU] = 3, /* 2 + 1 */
[GTP1_F_EXTHDR] = 1, /* 1 */
[GTP1_F_EXTHDR|GTP1_F_SEQ] = 3, /* 1 + 2 */
[GTP1_F_EXTHDR|GTP1_F_NPDU] = 2, /* 1 + 1 */
[GTP1_F_EXTHDR|GTP1_F_NPDU|GTP1_F_SEQ] = 4, /* 1 + 1 + 2 */
};
static int gtp1u_udp_encap_recv(struct gtp_instance *gti, struct sk_buff *skb)
{
struct gtp1_header *gtp1;
@ -279,20 +290,8 @@ static int gtp1u_udp_encap_recv(struct gtp_instance *gti, struct sk_buff *skb)
if ((gtp1->flags >> 5) != GTP_V1)
goto out;
/* FIXME: a look-up table might be faster than computing the
* length iteratively */
/* sequence number present */
if (gtp1->flags & GTP1_F_SEQ)
gtp1_hdrlen += 2;
/* N-PDU number present */
if (gtp1->flags & GTP1_F_NPDU)
gtp1_hdrlen++;
/* next extension header type present */
if (gtp1->flags & GTP1_F_EXTHDR)
gtp1_hdrlen++;
/* look-up table for faster length computing */
gtp1_hdrlen = gtp1u_header_len[gtp1->flags & GTP1_F_MASK];
/* check if it is T-PDU. */
if (gtp1->type != GTP_TPDU)

1
gtp.h
View File

@ -42,5 +42,6 @@ struct gtp1_header { /* According to 3GPP TS 29.060 */
#define GTP1_F_NPDU 0x01
#define GTP1_F_SEQ 0x02
#define GTP1_F_EXTHDR 0x04
#define GTP1_F_MASK 0x07
#endif