Errata

Chapter 3. BPF Maps - Working with BFP Maps - Iterating Over Elements in a BPF Map

In the output of the bpf_map_get_next_key() example where the map mutates:

Deleteing key '2' typo -> Deleting key '2' (extra 'e')

This map must be annotated with BPF Type Format (BTF) so the verifier knows how to intepret the structure -> typo "intepret" -> "interpret"

"zeccomp" is used instead of "seccomp"

In first sentence - "approaches this problem from an different angle" - "an" should be "a"

"raise in popularity" should be "rise in popularity"

Typo: "circustances" instead of "circumstances"

Typo using the name of the project Cilium (https://cilium.io), double 'L' is being used, whereas only one should be used.

DAG stands for Directed Acyclic Graph and not Direct Acyclic Graph

The paragraph mentions that conditions for rejecting the code follow, but the bullet points below mention the conditions the code has to fulfill for not getting rejected.

"The way a program structured" is missing "is".

Text refers to a ".BFT" metadata section. That looks like a typo for ".BTF". If it is not, that confusing difference should be called out in the text. This same likely typo is on page 82, second to last paragraph, "all of the BFT types".

Section header reads "Working with BFP Maps". It should be: "Working with BPF maps"

This paragraph suggest that multiple operations exist and some are described in the following two sections. Then, the next section starts with "The final operation we look at in this section".

Typo: "semaphone" should be "semaphore"

With the colon, the paragraph suggests that the map is declared below this paragraph and not above it.

"...as long as you don't mind loosing elements...": should be "losing" instead of "loosing"

"read the rest elements in the map" is missing "of the".

The last paragraph before the code example mentions that the map is populated with several elements, but in the example only one element is inserted.

Typo: "pbf_obj_pin" should be "bpf_obj_pin".

In the description of bullet (2), "pbf_prog_load" should be "bpf_prog_load.

"there is only a Ruby process running on our machine" should say "there is only ONE Ruby process running on our machine". As written, nothing but that Ruby process is running on the machine, which is obviously false.

The text should state that it is switching from Ruby back to Python for the next code snippet. It took me awhile to figure out what was going on.

"pbf_prog_load" this text has to be changed to "bpf_prog_load"

"You can also associate update elements in those maps" doesn't make sense, with two verbs in a row; the word "associate" seems to be spurious.

In the first sentence "A classless qdiscs is a qdisc" qdiscs should be singular "qdisc"

Second sentence "This means that is not possible to attach filters to classless qdiscs" "is" should be "it's"

This paragraph first mentions we can compile the program as we did before. But then, it mentions that we cannot compile this program in the same way.

The paragraph mentions that TCP packets are always dropped with XDP_DROP. But the next paragraph mentions another check for the destination port. Maybe, the "always do XDP_DROP" part should be removed.

Typo: "part contains our the list" should be "part contains the list",

In the "Seccomp Is cBPF" info box, "you might wondering" should be "you might be wondering".

In the "Seccomp Is cBPF" info box, in the first bullet list item, "registries" should be "registers".

In the third item of the bullet list, "and in Kubernetes, and a service virtual IP" should be "and in Kubernetes, a service virtual IP".