build: Allow to build astraceroute and flowtop without GeoIP support - netsniff-ng.git - A high-performance Linux networking toolkit

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author	Tobias Klauser <tklauser@distanz.ch>	2014-05-27 11:10:16 +0200
committer	Tobias Klauser <tklauser@distanz.ch>	2014-05-27 11:18:21 +0200
commit	98e21eb8633b31b006671735602df08d3f073261 (patch)
tree	12a25c68040a6e7718326cdf556dcc404e84380b /dissector.h
parent	47f41a76c7086761d0c64e743a5ca9f1b0e71440 (diff)

build: Allow to build astraceroute and flowtop without GeoIP support

Both tools are already prepared to handle NULL return values of the geoip_* lookup functions, so we might as well build them without geoip support if not needed/present. Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

Diffstat (limited to 'dissector.h')

0 files changed, 0 insertions, 0 deletions

alling bpf_skb_pull_data() to effectively unclone the skb from the very beginning in case it is indeed cloned. The heuristic makes use of a similar trick that was done in 233577a22089 ("net: filter: constify detection of pkt_type_offset"). This comes at zero cost for other programs that do not use the direct write feature. Should a program use this feature only sparsely and has read access for the most parts with, for example, drop return codes, then such write action can be delegated to a tail called program for mitigating this cost of potential uncloning to a late point in time where it would have been paid similarly with the bpf_skb_store_bytes() as well. Advantage of direct write is that the writes are inlined whereas the helper cannot make any length assumptions and thus needs to generate a call to memcpy() also for small sizes, as well as cost of helper call itself with sanity checks are avoided. Plus, when direct read is already used, we don't need to cache or perform rechecks on the data boundaries (due to verifier invalidating previous checks for helpers that change skb->data), so more complex programs using rewrites can benefit from switching to direct read plus write. For direct packet access to helpers, we save the otherwise needed copy into a temp struct sitting on stack memory when use-case allows. Both facilities are enabled via may_access_direct_pkt_data() in verifier. For now, we limit this to map helpers and csum_diff, and can successively enable other helpers where we find it makes sense. Helpers that definitely cannot be allowed for this are those part of bpf_helper_changes_skb_data() since they can change underlying data, and those that write into memory as this could happen for packet typed args when still cloned. bpf_csum_update() helper accommodates for the fact that we need to fixup checksum_complete when using direct write instead of bpf_skb_store_bytes(), meaning the programs can use available helpers like bpf_csum_diff(), and implement csum_add(), csum_sub(), csum_block_add(), csum_block_sub() equivalents in eBPF together with the new helper. A usage example will be provided for iproute2's examples/bpf/ directory. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>

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