Re: [PATCH v7 15/27] flow: Helper to create sockets based on flowside

[Stefano Brivio <sbrivio@redhat.com>]

On Fri,  5 Jul 2024 12:07:12 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> We have upcoming use cases where it's useful to create new bound socket
> based on information from the flow table.  Add flowside_sock_l4() to do
> this for either PIF_HOST or PIF_SPLICE sockets.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  flow.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  flow.h |  3 ++
>  util.c |  6 ++--
>  util.h |  3 ++
>  4 files changed, 101 insertions(+), 3 deletions(-)
> 
> diff --git a/flow.c b/flow.c
> index 6f09781a..2d0a8a32 100644
> --- a/flow.c
> +++ b/flow.c
> @@ -5,9 +5,11 @@
>   * Tracking for logical "flows" of packets.
>   */
>  
> +#include <errno.h>
>  #include <stdint.h>
>  #include <stdio.h>
>  #include <unistd.h>
> +#include <sched.h>
>  #include <string.h>
>  
>  #include "util.h"
> @@ -143,6 +145,96 @@ static void flowside_from_af(struct flowside *fside, sa_family_t af,
>  	fside->eport = eport;
>  }
>  
> +/**
> + * struct flowside_sock_args - Parameters for flowside_sock_splice()
> + * @c:		Execution context
> + * @fd:		Filled in with new socket fd
> + * @err:	Filled in with errno if something failed
> + * @type:	Socket epoll type
> + * @sa:		Socket address
> + * @sl:		Length of @sa
> + * @data:	epoll reference data
> + */
> +struct flowside_sock_args {
> +	const struct ctx *c;
> +	int fd;
> +	int err;
> +	enum epoll_type type;
> +	const struct sockaddr *sa;
> +	socklen_t sl;
> +	const char *path;
> +	uint32_t data;
> +};
> +
> +/** flowside_sock_splice() - Create and bind socket for PIF_SPLICE based on flowside
> + * @arg:	Argument as a struct flowside_sock_args
> + *
> + * Return: 0
> + */
> +static int flowside_sock_splice(void *arg)
> +{
> +	struct flowside_sock_args *a = arg;
> +
> +	ns_enter(a->c);
> +
> +	a->fd =  sock_l4_sa(a->c, a->type, a->sa, a->sl, NULL,

Nit: assuming you wanted the extra whitespace here to align the
assignment with the one of a->err below, I'd rather write this
(at least for consistency) as "a->fd  = ...".

> +			    a->sa->sa_family == AF_INET6, a->data);
> +	a->err = errno;


> +
> +	return 0;
> +}
> +
> +/** flowside_sock_l4() - Create and bind socket based on flowside
> + * @c:		Execution context
> + * @type:	Socket epoll type
> + * @pif:	Interface for this socket
> + * @tgt:	Target flowside
> + * @data:	epoll reference portion for protocol handlers
> + *
> + * Return: socket fd of protocol @proto bound to the forwarding address and port
> + *         from @tgt (if specified).
> + */
> +/* cppcheck-suppress unusedFunction */
> +int flowside_sock_l4(const struct ctx *c, enum epoll_type type, uint8_t pif,
> +		     const struct flowside *tgt, uint32_t data)
> +{
> +	const char *ifname = NULL;
> +	union sockaddr_inany sa;
> +	socklen_t sl;
> +
> +	ASSERT(pif_is_socket(pif));
> +
> +	pif_sockaddr(c, &sa, &sl, pif, &tgt->faddr, tgt->fport);
> +
> +	switch (pif) {
> +	case PIF_HOST:
> +		if (inany_is_loopback(&tgt->faddr))
> +			ifname = NULL;
> +		else if (sa.sa_family == AF_INET)
> +			ifname = c->ip4.ifname_out;
> +		else if (sa.sa_family == AF_INET6)
> +			ifname = c->ip6.ifname_out;
> +
> +		return sock_l4_sa(c, type, &sa, sl, ifname,
> +				  sa.sa_family == AF_INET6, data);
> +
> +	case PIF_SPLICE: {
> +		struct flowside_sock_args args = {
> +			.c = c, .type = type,
> +			.sa = &sa.sa, .sl = sl, .data = data,
> +		};
> +		NS_CALL(flowside_sock_splice, &args);
> +		errno = args.err;
> +		return args.fd;
> +	}
> +
> +	default:
> +		/* If we add new socket pifs, they'll need to be implemented
> +		 * here */

For consistency:

		/* If we add new socket pifs, they'll need to be implemented
		 * here
		 */

there are a few occurrences in the next patches, not so important I
guess, I can also do a pass later at some point.

> +		ASSERT(0);
> +	}
> +}
> +
>  /** flow_log_ - Log flow-related message
>   * @f:		flow the message is related to
>   * @pri:	Log priority
> diff --git a/flow.h b/flow.h
> index c3a15ca6..e27f99be 100644
> --- a/flow.h
> +++ b/flow.h
> @@ -164,6 +164,9 @@ static inline bool flowside_eq(const struct flowside *left,
>  	       left->fport == right->fport;
>  }
>  
> +int flowside_sock_l4(const struct ctx *c, enum epoll_type type, uint8_t pif,
> +		     const struct flowside *tgt, uint32_t data);
> +
>  /**
>   * struct flow_common - Common fields for packet flows
>   * @state:	State of the flow table entry
> diff --git a/util.c b/util.c
> index 9a73fbb9..f2994a79 100644
> --- a/util.c
> +++ b/util.c
> @@ -44,9 +44,9 @@
>   *
>   * Return: newly created socket, negative error code on failure
>   */
> -static int sock_l4_sa(const struct ctx *c, enum epoll_type type,
> -		      const void *sa, socklen_t sl,
> -		      const char *ifname, bool v6only, uint32_t data)
> +int sock_l4_sa(const struct ctx *c, enum epoll_type type,
> +	       const void *sa, socklen_t sl,
> +	       const char *ifname, bool v6only, uint32_t data)
>  {
>  	sa_family_t af = ((const struct sockaddr *)sa)->sa_family;
>  	union epoll_ref ref = { .type = type, .data = data };
> diff --git a/util.h b/util.h
> index d0150396..f2e4f8cf 100644
> --- a/util.h
> +++ b/util.h
> @@ -144,6 +144,9 @@ struct ctx;
>  
>  /* cppcheck-suppress funcArgNamesDifferent */
>  __attribute__ ((weak)) int ffsl(long int i) { return __builtin_ffsl(i); }
> +int sock_l4_sa(const struct ctx *c, enum epoll_type type,
> +	       const void *sa, socklen_t sl,
> +	       const char *ifname, bool v6only, uint32_t data);
>  int sock_l4(const struct ctx *c, sa_family_t af, enum epoll_type type,
>  	    const void *bind_addr, const char *ifname, uint16_t port,
>  	    uint32_t data);

-- 
Stefano